Acids do have some variety, some will melt things that others won’t. It might be that some form of acid out there could be contained in a paintball.
And yes, acid will take a lot longer to do its damage than kinetic energy will. Acid might be useful against hardened targets though. I could imagine that you could make a hole in a tankbot over the course of a minute with acid that you wouldn’t be able to make over ten minutes with a pistol… Acid also has more tendency to spread, though that is negated over any given period of time by the effect of multiple bullets, but might come into play if the target is highly obscured by splashing over a hand when it only hits a finger or hitting something above the target and dropping down… burn injuries tend to be painful, so there might be a persistent disability effect for some opponents. Finally, there are reasons why you would specifically want to use acid, but want to do it from a distance…
I guess acid also has the potential to be dangerous at very low velocities. The Acid itself is probably pretty obvious, and slow, so it isn’t entirely a stealth-weapon, but you could launch it with relatively little exposure og your position.
But yes, it would be a bad weapon when compared to a pistol…
