RE: homeprotection
This one's probably not as simple as it works, but I think some of the key points have been brought up already: 1) overpenetration, 2) "fright factor" associated with a pump shotgunand 3) stopping power.
If I were to buy a new handgun, I'd be looking at a .40 or .45, and have been really impressed with the Springfield XD. I already own a couple 9mms. After a year in Iraq, I won't recommend that caliber as anything but "last ditch".
I'm not a single guy with no kids though, and with that in mind, I think I'd have to vote for the shotgun, and preferably a 12ga pump, and I'd probably prefer a good turkey load over buck as has already been mentioned. Of course, I have a couple large dogs too. They raise the "unpredictability" factor significantly foranyone attempting to become my next lawn ornament.