I was more or less referring to a situation where you actually need to hang onto your weapon and get it back into a firing position quickly. Lets say you fall/slip, if you're experienced with firearms you should let go with one hand to steady yourself but keep the other hand on the firearm to make sure it's in a controlled direction and such. If you let go with your trigger hand it doesn't matter what kind of grip you've got, obviously. If you let go with your other hand though I'd have to say a pistol grip would be better, I stumble every now and then in the woods while hunting and the traditional style grips provide less of a control factor than pistol grips. I trip and fall quite often when playing airsoft when sprinting from cover and such, and it seems that a pistol grip is much easier to maintain control with.

That's my personal experience at least. Add that to the fact that I think they're more comfortable and I don't really have a reason to not use a pistol grip. The fact that shotguns have a higher barrel then rifles doesn't really matter if you know how to shoot properly.