Whew, a little heated in here. At any rate, a few quick thoughts:
1. A person should perhaps not say too quickly that he will take over-penetration any day, if he has children sleeping in the house. They will be the ones that will be killed or maimed. Two thicknesses of drywall makes for poor protection for your kids if you are shooting buckshot or slugs indoors. Imagine having kids asleep in two or three bedrooms upstairs, and letting loose with one or more 12 gauge loads of buckshot or slugs.
2. Last year in Memphis, an intruder was shot at 20 feet (down a hallway) with a single shot .410 loaded with bird shot. He was killed instantly. Although footpounds isn't everything, I believe that a 3 inch .410 packs about the same wallop as a 44 magnum.
3. I am sorry. But based on 35 years of shooting experience, I believe that a 12 gauge or a 20 gauge magnum, loaded with number 6 birdshot, would blow an enormous death-giving hole in anyone up to a distance of about 25 feet, and I don't care what type of clothes they are wearing. Maybe not with number 7 1/2 , 8, or 9, but definitely with no. 6. If you are really really worried about it, then go buy some no. 5s. Buckshot and slugs are simply not necessary for home protection. Remember, any time you start shooting a shotgun in a dark house, anything that can go wrong will go wrong.
Just my opinions. But, for those of you that are 50 years old or so, I am sure that you have seen many articles in gun magazines discussing this very same issue and reaching the same conclusion. Number 6 birdshot will do it.
Big Paulie