Brass Fetcher Ballistic Testing
 

check your defensive rounds
Handgun Ballistic Gelatin test results (22LR, 380ACP, 38 Special, 9mm, 45ACP)

its not what round you have, but where you put it.
on topic though, anything .380 and up in a good "plugged" JHP is solid enough to drop a person. if your trying to drop a man-bear-pig, then nothing short of 10mm +p+ JHP will do.