I have experimented a bit. Plasma accelerators are useless, they require more power, generate more heat, and the projectile moves at about the same pace as the cannon, while doing the same dmg. Also the projectile costs are ridiculous. Gimballed cannons are alright, though you wont hit anything smaller than an Asp with them in combat. I would use railguns but for their pathetic ammo capacity, I mean 30 shots, really? Come on.
I don't really like multicannons, they make an annoying sound on impact.
Also missiles are still bugged, 50% of them fly backwards.