"if you're up to you chest in a rice paddy, and taking fire from the jungle, you want a gun that'll go THROUGH the tree, THROUGH the badguy, and then KILL the guy guy standing behind him."
M1A
Not sure that this is a great selling point for a home defense gun, ie neighbors, family in other rooms, and not knowing where the bullet is going after it goes through the intruder...Over-penetration is also a problem in home defense scenarios with an AR15...(refernce the box o' truth website)
Shotguns will work for home defense, put they are not the ideal. Shotgun follow up shots are not as fast as either semi-auto listed in the original posts question (Especially with 3" buchshot max dram loads). Many may say, it only takes one shot from a shotgun to end the encounter: just remeber how easy it is to miss at 3am with the lights off and your half asleep.
Also, many believe that racking the slide to load a shell is enough to scare away an intruder
...again, not a great selling point announcing your position in the home....Bottom line for home defense, use what you are familiar with and know its strenghts and weaknesses and use that info to your advantage in defending your home. A snub nose .38 is better than a locked up rifle that takes 2 minutes to get to that is located in the basement and you are in your bedroom.
But hey, I'm just glad that many people are firearm owners and we have the freedom to speak and debate topics like this.