your wrist cocked at a downward angle(standard contour stocks) causes muscle tension which can prevent proper trigger discipline while also requiring more 'chicken wing' positioning of the firing arm. this not only creates a less comfortable grip but also reduces the amount of pressure that can be exerted on the firing wrist, this means more recoil delivered to the shoulder.
The "chicken wing" position of the arms is what allows you to easily and quickly swing the gun on a target. I'll disagree about the comfort, as I find it MUCH more comfortable - I can hold a shotgun horizontally with one hand much easier than with a vertical pistol grip. That grip makes any gun very front heavy and difficult to hold horizontally (as you would towards an attacker)> Personally, my shoulder is bigger and meatier than my wrist, so i would rather the recoil went there and to the fragile bones in the wrist