One of my favorite old tag lines I saw somewhere.
"A 9mm may expand, but a .45 won't shrink."
If'n I'm gonna be heaving slow rocks, I'd just as soon they be heavier. d;^)
Given that no pistol is a "death ray", doing whatever you can to increase your odds is always adviseable. But if the boss says I get an M9 with FMJ, then I just have to make it work.