Actually, the 9mm with the right load does just as much damage as the .45 ACP. And for a home defense load in your 12 gauge #1 or #4 buckshot it better than 00 buck.
Here are a couple of good sources:
9mm Vs 45 and others.
http://greent.com/40Page/ammo/9/9mm-advoc.htm
12 Gauge rounds
http://www.firearmstactical.com/briefs10.htm
I guess the main theme of this article is that IF the 9mm bullet deforms to a .50" hole, and it penetrates effectively, then it will be as good as the .45.
Didja ever shoot anything whit any of this stuff? If you did, did it bleed and could it shoot back?