There's nothing wrong with a 9mm, if you take the time to learn how to actually shoot it. James Butler Hickok 'put paid' to more folks than most of us will ever have to deal with, even in our 'wildest' nightmares, and he did it with a pair of 36 caliber Colt Navy cap & ball revolvers. How did he do it? He hit what he was shooting at. Period.
Do I have anything against larger calibers? Not at all. I have owned (and in some ways prefer to my 9mm Ruger) .44 Special, .45 ACP, .45 Colt, and .476 Webley revolvers (the .476 was the most fun ;>). But that's more a matter of my preference for revolvers (which is based on my appreciation for history, and the 'KISS Principle' ;>)...
Accuracy is always #1.
After that it’s stopping power.