Lol the great Train Loop Debate
I hope in Uncharted 3 the enemies can't take so many bullets. Really my main complaint about this series (and many other games). Even wearing Kevlar, getting shot by an AK-47 or M4 would do more than cause you to lose your footing
The rifles had the same issue in UC1. Esp the AK. The first few bullets are just to hurt their feelings, it'd seem. In the first one, the big pistol was the best to use. In this, the Deagle is really good for all ranges but you don't get it often. The Pistola sucked, I thought.
I think they do it primarily to extend the gameplay. Imagine if the rifles were like CoD and you could quick kill. You'd fly though the game and the cover aspect would make it real easy. This way you're forced to fire at one enemy repeated times while you're being shot at by others.