The best weapon for home defense is a shotgun. The are several reasons. It gives you a second option if your not inclined to wait for them to actually enter your house (Nothing says hello like racking a shotgun round as they are attempting to gain entry). Your drywall should prevent most collateral damage. Finally you don't have to be a sharp shooter to be effective.
The type of weapon has nothing to do with prosecution for shooting the burglar (no such thing as overkill, dead is dead) however you do have some responsibilty for rounds that may strike your neighbors kid sleeping in their bed. An AR should be an option only if you have no other.
When I first read "shotgun" I was praying you would NOT say that...
IIRC, .32 00 tends to penetrate walls farther than .223...