A gauss gun, if it were sufficiently cooled and powered (I'd say power supply should be integral in the magazine for logistic's sake) would be a very versatile weapon.
Ammo storage would be more efficient as there'd be no need for propellant, but the projectiles would have to be massive (not big, just massive) to do any damage and would add a lot of weight. Any gauss gun would probably be able to beat conventional slugthrowers in velocity and range easily, but they would not be completely silent as the sonic boom from the projectile going at hypersonic speeds would make a loud crack. Alternatively, the operator might be able to "turn it down" using a switch and fire at subsonic velocity only, and maybe even lower so it works like a dart gun.
Heat dissipation and power supply are the biggest obstacles right now, I believe.