There's also the "fire and forget" aspect of the swarm, you can pop off a volley at a vehicle quick swap to your sidearm and kill incoming infantry and back to the swarms to continue the assault (I've done this as recently as tonight to great effect).

I don't see what you're getting at. You want me to factor in the chance of a hit? The Swarm Launcher does all the work for you, there's only fire interval that can be calculated and reload time, but that doesn't change the damage you've dealt. Elaborate.

Why are you bringing the HMG into an AV discussion?

The HMG will only ever have 38% damage efficiency on any vehicle (possibly less for tanks and DS, I dunno), so it doesn't actually function as an AV weapon in any capacity.

It also relies on pure RoF and medium range engagements to pull off significant damage while both the FG and SL are on-hit damage weapons that, if you're good enough, really ought to be hitting every time.

Incorrect, all weapons do not have this effect equally. The Laser for example does not have it at all.

Keeping things in the Forge vs Swarm context however, swarms track their target with no further input from the user meaning you release the trigger and are done. The lock means that you can start paying attention to lining up your shot/taking cover where as with the forge the impact of the shot is more or less instant meaning you have to keep your focus and your aim directly on the target rather than incoming infantry support.

Further the light weapon slot is top of the selection wheel making it an easier/faster swap than the heavy which is directly across from the sidearm (this won't matter so much for a KBM user but for anyone else those seconds are relevant).

Beyond all of that your movement speed with a charged Forge is much slower than with a swarm, making the return to cover/avoidance of incoming support fire all the more difficult.

As far as the 'contrails' are concerned, fire then move (while locking on) and fire again from another position. Something that one should be doing when using swarms. forge, or sniper. The swarms however have the benifit for being able to somewhat mislead the opposition because you can be locking your second shot while on the move something that the sniper and forge cannot do with any great effect (forge in large part because you can't move at a rate notable enough to make your change in position very relevant/effective).

0.02 ISK
Cross

EDIT: redline sniper, until you can engage in a mature discussion of the issues rather than ignore the majority of what I've said while (inaccurately) harping, in a snide manner, on an aspect of a single point I raised I'm going to cease responding to your posts as such responses are obviously not being read and thus a waste of my time.