Pistol grip changes your hands access to the guns mechanics like safety and action release lever. Consider these changes.
-STD Stock is decent for average people
-Stock+Pistol grip is like STD Stock but better and can be fired rambo style (w/o pressing stock to shoulder)
-Pistol grip is good for home defense and close up action only... You can't aim as good and shoot steadily but it won't matter if someone's accross ur living room.
-Pistol grip w/ foldout stock is GREAT if you like firing the gun rambo style AND occasional normal style but usually the stock is hard and kills your shoulder over time
You need maneuverability for home defense like you said so if the gun is home defense and you don't ever do a lot of repetetive firing (like at a range) then go w/ a folding stock.
Folding stocks are illegal on semi-automatic shotguns in california and a FEW SPECIFIC shotgun models... They might harras you but tell'em to ask some guy named "Hanz" (j/k that's only in Santa Barbara late night)
Anyways this is what I use and here is what I've got to say:
http://www.knoxx.com/NewStyleKnoxx/Products/COPstock.htm
It's great, pretty solid (not quite solid enough), nice and stylish, useful, and it reduces size so it's convenient to carry BUT
It hurts like a motherb!!!! when you fire several breecher shots w/ the stock open against your shoulder and no good for shooting around (like as a hobby) so use it for defense only!
If you have a hobby just have 2 diff stocks or guns but it's not worth using the COPStock for hobby
check out
www.Knoxx.com
The CompStock is SAID to be the best stock ever (least recoil) for heavy duty fire! anyways I'll update my post later! G2g
Hope my rambling helps you in your decision!