Worth elaborating: If all religious people were non-hypocritical and do exactly what the religion they claim to follow commands, there would probably be an enormous initial drop in violence, followed by any religions that follow commandments like "thou shalt not kill" without exception being wiped out, with religions advocating holy war and the persecution of heretics getting the eventual upper hand (although imperfectly adapted religions might potentially be able to hold off the better-adapted ones through strength of numbers- for instance, if a large area was controlled by a religion with the burning of heretics and defensive, cooperative religious wars, they could hold off smaller nations with religions advocating offensive wars).

One good thing about hypocrisy is that it makes a massive buffer against certain types of virulent memes. On the other hand, a world where everyone took a burn-the-heretics interpretation of Christianity or Islam 100% seriously would certainly have some advantages over ours, and especially over our middle ages- things like no un-sanctioned killing, most notably, no wars against others of the same religion, etc. Probably lots of things that would be decent ideas if you could get everyone to follow them, at the cost of an occasional burnt heretic (and possibly constant holy wars, until one religion gains the upper hand and overwhelms the others).