physics actually work there. have a fat guy, skinny guy, and a buff guy get into three different but similar car accidents. the fat guy survives over the other two as he has more cushion for his organs, so he can absorb more impact.
now shooting them in the head is something different...
i personally didn't have any issue with the uncharted physics. but i did have an issue with their repetitive combat system. sneak. shoot. hide. sneak. punch. hide.
There'd probably be a difference in body shots, but not as much as is represented in the game. If that were the case I wouldn't feel so apprehensive about walking through bad neighbourhoods.