Bar could use a reload nerf. And maybe a slightly slower rate of fire. I bought mine because of the damage and speed. Souizen doesn't really need anything done to it, it's perfectly fine IMO. PBP needs a bit slower rate of fire. And i think that's it.
An increase in health would be nice, but not too large. 75 sounds great.
But if health is increased, I don't think that damage should be increased.
Gotta keep in mind price differences, because they should make a difference, but not a crazy large over powered difference.
Honestly, I think things are pretty fine as they are, and the nerfs mentioned above are just little things to balance a little bit better. But it's all opinionated.