I've cited the Ellifritz database before. It's not the DEFINITIVE source of round effectivness, but its the best I've found, thus far. Here's a link:
http://www.buckeyefirearms.org/node/7866 Hopefully Ellifritz will be able to continue collecting data over time.
We know that the data collected for this study is skimpier for some rounds than others, and that aspect of data analysis can cause us to make invalid conclusions, but these results do suggest there's more "there" there than some might want to acknowledge. You'll see that .357 Magnum remains one of the more effective rounds -- but there's about the same amount of data for .357 as for .380... The 9mm round was the most used, and was pretty effective, too.
This study doesn't show barrel length, which must be a considered with any handgun: if the barrel is very short, too much of the round's powder with most loads (unless the round is speciifically cooked up for short barrels) will follow the slug out of the barre (unignited) before it has contributed to force of the shot.
That said, the .380 round does well in the data shown, when compared to the .45... I was surprised:
.380 vs. .45
# people shot: 85 vs. 209
# of hits: 150 vs. 436
% of fatal shots:
29% vs.
29%
Avg # rounds until incapacitation:
1.76 vs. 2.08
% shot but not incapactitated: 16% vs
14%
one shot stop:
44% vs. 39%
Accuracy: 76% vs.
85%
% incapacitated with one shot:
62% vs. 51%
It got me thinking that a longer-barredl .380 (perhaps like the Beretta 84) might be a better gun for some folks than some of the other guns, as a larger .380 is likely to be far easier to shoot well. That would NOT be the case with the true "mouse" guns, which can be a challenge for even experienced shooters. (I'm not saying they can't do the job, only that it would be harder to use them to do the job...)
You can't accept what's shown here as gospel, but you can't say it's meaningless, either.