I've really enjoyed this thread. Interesting comments by some folks who have obviously studied the 'shotgun for home defense' issue and carefully formulated a plan. Opinions aside, having any loaded gun is infinitely better than having no gun when you need one.
For whatever it's worth, I've struggled with this question for years. I keep a Mossburg 500 (20" barrel, extended magazine) stoked with four #6 shot game loads, followed by one 00Buck followed by 2 slugs. I keep the chamber empty with the thumb safety on. I have additional 00Buck and slugs nearby. I have several loaded & large handguns nearby.
[Although not sensitive to handgun recoil, I don't like rifles larger than 30-06 and 12 gauge slugs kick the dog out of me (when shooting at paper targets). However, I don't recall ever feeling any recoil when shooting elk, deer, etc. or when qualifiying at the police range. So I'm not sure the tactical low-recoil loads are necessary].
I too, am concerned about penetrating drywall (sheetrock), thus the #6 shot. I also keep electronic hearing protectors by the gun 'cause I'd like to preserve my eardrum when the gun goes 'boom' in the house.
I don't think we are ever going to resolve what's the best load for H.D. shotguns.
My $.02
