I prefer the big bore, but often carry something smaller due to dress. I carry the big bore because it has more stopping power, or does it?
A while back I read of a police officer in Jackson,MS that shot a bad guy from about 40 feet with a .40 caliber handgun. The perp had already shot the Cop twice, once in the arm, once in the stomach. The perp was carrying a cheap .25 auto. The perp walked away, the cop died on the spot.
We have read the FBI reports pertaining to the Florida shoot out with a group of bank robbers, several of which were hit in the vitals area numerous times with .38s and 9mms. A couple of them lived. I sat on a jury a while back where a man was killed by a .22 short from a "Saturday nite special." The shooter was about 30 feet away.
You can go on, and on with similar stories. The point is, sometimes it makes no difference what you are shot with, all of them can kill. Selection of caliber is really not as important as how well you handle what you are carrying.