Whilst in the Army a few years ago..., feeling old now.
I had to use a 9mm on a few occasions against enemy combatants. I was very unhappy with center-of-mass shots. Head shots always seemed to work fine, but in real-world scenarios, center-of-mass works best for me. Just a lot easier to hit.
While resupplying one time, I was talking to the armorer about my displeasure with the 9mm. He said he had some older 45's and plenty of ammo, if I wanted to give it a try.
A few weeks later I got the chance to try the 45. Impressive is not an understatement. One-stop-shot pretty much sums it up from my experience.
I was taught double-tap center of mass, then one head-shot. But "most" of the time, if I was using my pistol, it was cause I didn't have time to re-load my rifle. So I didn't "unload", as I was trying to save ammo.
So without getting to grotesque, I think the 45 is without a doubt, a much better man-stopper than a 9mm. Personally, for concealed carry, I will never own anything else.
Also, let me just apologize in advance if what I have said seems to harsh, as I was trying to write it as non-offending as possible.