If the .380 ACP is inherently less effective at stopping a bad guy in real life situations (not gelatin bad guys) compared to other common carry calibers like 9mm, 38spcl and 45ACP, you'd think it would show up among this collection of data, but it doesn't. The results among these calibers are eerily similar. Significant differences in failure to incapacitate seems to generally break with calibers either smaller than .380 or with magnums, higher and lower rates of failure to incapacitate.

An Alternate Look at Handgun Stopping Power | Buckeye Firearms Association