I use all three, AMMs, gauss and lasers. AMMs are nice because of their range; I shoot for a 3 mkm range with my AMMs. It needs a larger investment in FCs and missile sensors, but pays off (I feel) in how many salvos I spend per missile. It's also a good last-ditch weapon as it vastly outranges beams, making it good for hitting smaller craft or sandpapering enemy armor to prep for close combat. Gauss cannons spit out a lot of rounds very cheaply making them very, very good against large missile swarms. So AMMs can deal with larger missiles, gauss take care of missile swarms and leakers. Lasers then are dual-purpose, even the smaller sizes can dish out a ton of damage at JPs or any other close-range scenario. When they aren't nailing enemy ships they're good area-defense weapons. They're also better against armored missiles.