It's really a ship-type-versus-ship-type sort of thing. Even if two ships have the same "shell" type of ammo, it's assumed that they are subtly different in construction of ammo (caliber, what have you). In the case of lasers, different construction of the firing mechanism, power levels, this that and the other. And for the hulls on the other end, I've pretty much covered that already I think. So the net effect is that every ship is assumed to have a subtly different ammo type, and a subtly different hull type, and the simulation is how all of those things interact.
Of course, the general ship classes (autocannons, tanks, whatever) all share a huge number of characteristics amongst their levels, even if the balance at each level isn't quite the same (same as the relative performance characteristics of a 98 civic and a 2000 civic are different by a bit).
And, similarly, the different ammo types (shell, ammo, missile, etc) all have some similar characteristics, especially when it comes to specific immunities (immune to sniper shots, or minor electric shots, or whatever), or when it comes to absorption of shots (absorbing lasers on deflector drones), or when it comes to counter-shooters (counter-missile turrets, etc).
So, there are some overarching meta-classes to make things a bit simpler compared to what they otherwise would be, but each unit is subtly unique all the same.