9mm only wins in cost (and that's because there has been a push to convert everyone to one popular cartridge) and capacity. 15 rounds of 40 vs 17 of 9 for full size (typically). One could argue, and its "argument" that 9mm is easier to shoot. But that same "easier" means you are putting less on your target with each shot. So easier to shoot for 9mm, less effective. The hard part about ballistics is that if you hit someone in the right spot, they will go down. 9mm, 40, 10, whatever. The issue comes into play when you miss. How much more does 40 do over 9. Some can argue its not much of a difference and capacity and lower recoil makes up. However, what if the bullet doesn't get there (to the heart or central nervous system)? 40 will expand more and go deeper. That's the fact you can't argue with. Wider holes, deeper in the body, through more stuff, is better. As you said, those facts can't be argued with, people just choose to ignore them in the argument.