Boy, I'm probably going to get torched for this one but, here goes.....
I'm not crazy about pistol grips on a shot-gun, especially if it's for home defense. I think it was solution in search of a problem that the manufacturers were happy to cultivate in order to sell some product. They're just a whole lot tacti-coolier than a standard stock right?
For a home defense shotgun I view them as a drawback. You watch the idiot box and generally when someone is moving through a doorway with a shotty it's with barrel almost straight up, and stock down. If the badguy were to step out and grab that barrel you'd have a hard time bringing it back into play.
A different school of thought is to move through the doorway with the barrel down, stock up. If someone were to grab the barrel and try to keep it down, you could always lever the stock down, which will automatically start the tip of the muzzle moving up. At the very least you could probably pop someone in the knee. I think it would be pretty tough to do with a pistol grip shotgun. Ergonomics just aren't right.
Plus, executing the butt stroke is a whole lot smoother.