“9mm vs .40 vs .45: Which Chambering Has More Stopping Power?”
“the best a 9mm could do was 67.5 percent.
The .38 Special fared just as poorly, and the standard FBI-issue .38 Special [158-grain, lead, hollow-point +P] also achieved a 67.5 percent success rate. Among the initial rounds tested, only the 10mm, .45 ACP and a single .357 Mag round were able to score consistently above 90 percent.”
“https://www.personaldefenseworld.com/2017/03/9mm-40-45-acp-stopping-power/";
Actually I believe that accuracy of the person shooting determine the outcome. I think if they did manage to ban high capacity mags of 10 or more then they would decide 40 S&W and 45 Apc and larger pose a hazard of missing the target and hitting a snowflake they would then try to limit magazine to 9mm max and 7 rounds max.
This is based on a study done nearly 30 years ago. The difference in ammunition then and now is drastic and ammunition matters.
The FBI has concluded that the slight advantage in "stopping power" (whatever that term really means) by larger calibers, is far overshadowed by having greater magazine capacity. This is the reason they dumped the .40. You need penetration of at least 12 inches in ballistic gel. Once you're there, the diameter of the round is not the deciding measure.