I was originally going to post this with the ship comparison guide, but was worried that it would get too long and into tl;dr territory, so instead separated it out into a shameless and easily Google-searchable attempt to fish for more hits before my blog goes back into enforced hiatus, when I have to go back to doing my real job in a couple of weeks. The real beauty of Elite: Dangerous is that there's no 'proper' way of playing the game - you just have to find out what works for you the best. But that's not to say that a little bit of help is unwelcome, so here's my take on the advantages, disadvantages and potential uses of the currently available ship weapons in the Elite: Dangerous beta. Make of my thoughts what you will - your mileage may vary (as the saying goes).
I'll start by describing the weapon types themselves, as there's quite a lot of variety with what you can play with, both in terms of weapon type and also their hardpoint mounting type, all of which have profound implications on whether they are suited for you (as a pilot) or for the ship you are flying. The first question to answer when considering your weapon loadout for your ship is what type of ship murder hardware do you want to use?
The currently available weapon type are: laser, cannon, multi-cannon, rail gun, missile and plasma accelerator.
Lasers are available in pulse, burst, beam and stealth variants (though I have not seen stealth lasers for sale in Beta 1 - perhaps I've not been lucky enough to come across one on my travels.) Lasers are particularly effective against shields and less effective at causing hull damage, but have a advantage of being cheaper than the other forms of weapons, making lasers the default go-to weapon when equipping your ship.
Pulse lasers, as the name suggests, fire in short, high-powered stabs of coherent light. They have the advantage of concentrating the power of the weapon into pulses, rather than firing over an extended period of time, meaning that the power drain and heat generation of the weapon is low, while the relative damage done is high. Pulse lasers are therefore best used on ships where power plant capacity is low and where heat generation needs to be carefully managed, or where ships have many hardpoints that can be fired simultaneously. You will typically see pulse lasers being used by small fighters, such as Sidewinders, or in turret form on ships like the Type 9 and Anaconda. Pulse lasers are generally considered to be entry-tier weapons for pilots who aren't terribly adept at keeping enemies within their sights and require a weapon that can be fired repeatedly over a long period of time before making your power plant melt. Any pilot worth their salt, and able to afford it, will quickly ditch pulse lasers for more effective weapons.
Beam lasers are more advanced, yet also more difficult to use effectively than pulse lasers, as they are capable of firing in continuous beams for as long as you keep the trigger depressed. You might think that beam lasers would do more damage than pulse lasers, but this isn't necessarily true. Beam lasers (in the current build) seem to be underpowered in terms of inflicting hull damage, compared to pulse and burst lasers, yet generate heat far more quickly. A beam laser in thermal overload is a dead weight in a dogfight, and using beam lasers often requires you to constantly micromanage your weapon power setting, balancing and rebalancing it with the other systems, so that they don't conk out just when you're about to line up the killer shot. Admittedly, beam lasers look very sexy as you walk them over the hull of your target, but these aren't the beam lasers of Freespace 2 or Babylon 5 that carve off slices of your opponent - and more's the pity! I can't honestly recommend using beam lasers unless Frontier re-tweak the damage versus heat generation relationship. Turreted beam lasers in particular are an outright liability, thanks to their drunken targeting. They're more likely to cause you to blow up than your enemy. Avoid at all costs - at least for now.
Burst lasers are my personal favourite from the laser weapon pantheon, as they're a good halfway house between pulse and beam weapons. They operate by firing Hicks-style, potentially dealing more damage than pulse lasers, without the massive overhead of heat generation you have with beam lasers. They are also cheaper than beam lasers and multicannons, so if you're after a weapon to strip the shields from a target, while you have another weapon to take care of the hull, burst lasers are the way to go. Burst lasers are especially useful in gimballed form on Class Two mountings, so work especially well on Sidewinders and as secondary weapons on Vipers and Cobras. The power requirements, however, are too high to make them much use on Eagles, which is unfortunate.
Stealth lasers are weapons that were in Premium Beta, but I'm not entirely sure if they have been removed from the Standard Beta, as I've not seen one. Stealth lasers work in essentially the same manner as pulse lasers, but without the heat generation (or the sound effects), and as you might expect, are very rare and very expensive. If you can find one, or if you know for sure if they've been hit by the nerf cannon and been removed from the game, please feel free to let me know in the comments.
If you have a Cobra, Viper or something smaller and want to make ships go 'splode!, then you're going to want to know about cannons. As you can see in the picture above, cannons make ships go 'splode! very, very well indeed. They're massively powerful, have a low power drain and heat generation rate, plus they're really cheap. They do have their shortcomings, however. One, they've only got a clip capacity of five shots prior to reloading and their reload rate is really quite slow, so you have to pick your time to shoot very carefully. This is doubly important, because cannons are currently only available on fixed mountings and it is unlikely that they will ever be available on gimballed or turret mountings, for game balancing reasons. This makes cannons a real skill-based weapon, as the low fire rate and aiming issues mean that a moderate pilot will have a lot of difficulty hitting targets with cannons at distances over 1000 metres, though it can be done, if you are good at anticipating the way an enemy will move. Cannons do so much damage that you don't even need to bother with a shield-stripping weapon like a laser. A cannon-equipped Viper will take down a small fighter in two volleys and larger ships like Type 9's and Anacondas can be taken down from full hull health with a triple cannon-equipped Eagle very easily indeed. The cannons will probably be tweaked in future patches, because they do make combat just that little bit too easy, if you're a good shot.
Probably the best all-round weapon for the budding combateer is the multi-cannon. Originally, I wasn't much of a fan of the multi-cannon, due to the spin-up time before firing and I preferred the immediacy of laser weapons, but as I've had more practice using them (especially the gimballed versions), they're arguably the best balanced weapon in the game. While multi-cannons are more expensive than lasers or cannons, the extra cost is worth it, as nothing is better suited to ripping through the hull of some poor greenhorn in a Sidewinder than a multi-cannon. Nominally, projectile-based weapons such as the multi-cannon are supposed to be less effective on shields and more damaging to the hull of a ship, but in practice, an all projectile-based weapon loadout is just as quick at getting kills as a mix of multi-cannons and lasers. Having both weapon types in your loadout does ensure that your ship will never run out of ammunition, however! As with the cannon, multi-cannons require you to lead your target, as unlike a laser, it takes time for the projectile to travel the distance between your ship and the target, which means that if you're not a decent shot with a fixed mounting, a lot of your ammo is just going to sail off uselessly into space. Investing in the more expensive gimballed versions is a good idea, as the damage reduction in power loss is more than made up for by the enhanced target tracking ability of the weapon. Gimballed multi-cannons are especially effective at suppressing the regeneration of a target's shields, as well as getting the enemy pilot to gradually panic at the gradual erosion of their hull integrity, your bullets nibbling away percentage point after percentage point. The best thing about multi-cannons is that they have the best trade off between weapon damage and heat generation, so you can essentially keep firing until you run out of ammo, making extended, multiple target engagements far more manageable. The ammunition is plentiful (like the cannon, 2100 rounds per gun) and cheap to replace, so you should be able to rip through at least 15-20 targets before needing to head back to base for rearming. You will find multi-cannons on pretty much any ship within the game, and you will want to be wary of any Lakon Type 9 Heavy or Anaconda equipped with turreted multi-cannons: mess with them at your peril!
Rail guns are the next class of weapon you might want to consider, being one step up in both cost and damage from the multi-cannon. I've only really used the rail gun in the single player scenarios, and I've yet to be convinced by them. I have encountered other players (and, indeed NPCs) that use them, but they appear to be even more of an 'all or nothing' weapon than the cannon. Rail guns are capable of dealing massive amounts of damage (I've seen NPC Cobras been taken down in two double hits of rail guns from another Cobra or Anaconda), but that massive damage potential comes at the cost of huge amounts of heat generation. Rail guns on Eagles or Vipers are a singularly bad idea, because the power drain is so high that deploying them will likely shut down luxuries like your shield or drive system. I have seen many rail guns used on Sidewinders and Cobras, but the fixed mounting and the long time delay before firing reduces their effectiveness to slow moving ships at close range, and few enemies (even the low bounty, low quality NPCs) are so obliging. I'm sure there are people out there who will swear profusely by their love of the rail gun, but I'm not one of them. Definitely try before you buy in the single player scenarios.
As discussed in my ship comparison guide, missiles are highly damaging, yet massively expensive weapons that are most commonly used by players as 'worry about this while I bugger off into supercruise' weapons. The biggest problem with missiles isn't their limited ammo capacity (12 per rack for Class 2 launchers and 24 per rack for Class 4 launchers), it's the fact that they cost 10,000Cr per 12 missiles to reload. Financially they're unjustifiable for any pilot who wants to make their money through combat missions. As a last resort or deterrent weapon, I suppose missiles have their place, but you can get quicker kills on small ships with cannons, and unless you're flying an all-missile armed Anaconda, it's unlikely that you'll ever be able to kill an opponent with a single volley of missiles, reducing their utility as a 'fuck off and leave me alone' weapon. Unless Frontier reduce the cost of the missile reloads, I can't see too many combateers systematically making use of missiles as primary weapons.
Lastly, we have the Plasma Accelerator, which as a weapon requiring a Class 8 hardpoint, is currently only the preserve of players who have Anacondas. I'm not (yet!) one of these lucky people, so I can't comment directly on the user experience of having one. I can, however, comment on the experience of being on the wrong end of one (THANK YOU, COLOSSUS!) and that comment is "OW! FUCKING JESUS MOTHERFUCKING CHRIST, OW! WHY DID YOU DO THAT, YOU FUCKER?!?" I hope that was useful to you in some way. (Suffice to say, they're really rare, expensive and do lots and lots of damage)
[Edited Addendum: I've had a chance to use one for myself now, and while they might cost nearly 800,000Cr and be pretty hard to find, holy crap, it's worth it to be able to one-shot anything up to and including a Cobra Mark III. They're like cannons on steroids. Wow. Next time I meet Colossus, he's going down in plasma flames.]
This just leaves us with the quandary not even The Bard himself could resolve: To gimbal, or not to gimbal, that is the question. I'm paraphrasing, naturally...
'True' combateers (the type of people who like to call themselves 'hardcore' - you know, 12 year olds...) will extoll the virtues of fixed weapon mountings saying that they make the combat more challenging and that as fixed weapons are more powerful than their gimballed counterparts they can achieve faster kills. While it does pain me to admit it, they do have a point. Once you've flown a Viper with four cannons and seen how quickly and easily it can dispense with just about any ship in the game you will ask yourself 'why would I want to use anything else?'. This, however, is a position you can only adopt after you've put several dozen hours into the game truly mastering the flight model and controls, gaining a couple of hundred kills along the way. Give the same ship and loadout to a brand new player and their reaction is most likely to be 'How the bloody hell do you hit anything?'
I've got over 400 kills in the game and while I'm as vociferous an advocate for the all-cannon loadout on fighter-class vessels as you'll find, I still find gimballed weapons useful. I would have found getting into the combat far more demoralising and difficult had it not been for the gimballed weapons, and for a long while my preferred combat loadout on the Viper or Cobra was two C3 Gimballed Multi-cannons and two C1 Gimballed Burst Lasers. Even now, I'm experimenting with a mix of three fixed cannons and one C3 Gimballed Multi-cannon on my Cobra (or Viper) to finesse my damage output, suppress enemy shield recharging and get even quicker kills than with four cannons alone. There's so much depth in the combat model that you can't really say that there's one 'true' way of playing the game. In short, you gimbal if you want to.
I'll save commenting in detail about turrets until I've gotten enough money to kit out an Lakon Type 9 and I've used them more extensively, but I will say this: Don't use them on Cobras or anything smaller. Save yourself the insurance costs...
In summary, then:
1) In the beginning, use the fixed pulse lasers on your free Sidewinder to build up experience and confidence in combat and the flight model.
2) Try to avoid beam lasers, even if you're a very good shot - you'll get a better damage vs. heat return using cannons or multi-cannons.
3) Gimballed burst lasers are really effective - buy them as soon as you can afford them, so that you can get easier kills and approach combat with a feeling other than trepidation. Where possible, use them in tandem with gimballed multi-cannons to have an effective shield-hull double-whammy combo.
4) When you can afford a Cobra or a Viper, a mix of fixed multi-cannons and gimballed burst lasers will have you committing space murder faster than you can say 'Richard B. Riddick'.
5) Ultimate space badasses, though, only use cannons.
Good hunting, commanders!