I remember seeing an episode of guns and ammo where they were testing the over penetration aspect of different firearms and then used those firearms to fire in ballsitics gel. Pretty much what came about is that a shotgun in an averaged size room was more than lethal with the less amount of penetration. I think the birdshot went through one wall and didn't go all the way through the other. Where 9mm went through all the sheetrock walls they had hung up (studs too). 45 ACP actually penetrated less than the other handguns and of course slugs went through everything as well. I can't remember exactly how far they were shooting, but I was thinking it was 15'. Anyway, With the birdshot they were using they got plenty of downrange energy on target with plenty of penetration in the ballistics gel...
After seeing that and reading some of the other posts on here, I would say that birdshot would be more than adequate for HD in MOST homes. If you live in a mansion with huge rooms then maybe you should look elsewhere. If you can afford the penetration aspect of different self defense rounds, then maybe go with buck shot or slugs, or get a good handgun or carbine. If not, hit the spopt you want to hit and pray for the best outcome for you and your family.