Personally, i don't see much difference between the MP40 and the PPSh.
What i dont get is all this MKB moaning:
Allright, it just might not be historically accurate, but in terms of balance it is totally fine.
The MP40/PPSh are more stable, but deal lower dmg.
The SVT/G41(?) (which are imo (!) the best weapons in the game) are more accurate but hold less ammo and are semiauto.
The MKB is the middle between both, having a bigger recoil.
The AVT however is imo (!) by far the worst rod this game has to offer as long as you use the crappy burst fire mode. If used in semi-auto it's basically a SVT and thereby adorable.
For ppl who want to revive the WW2 in its most proper way it might be a pain in the patootie to see everyone running around with those guns, but for me, who just wants to play a nice tactic-shooter it's totally fine.