I'll throw in my .02 I guess.
1) Let us remember... we are talking about handguns. They are *defensive* only 99.99% of the world. If you are using a sidearm, you are already in a bad place. Handguns (all calibers) are weak and underpowered. We carry them for convenience (light & small), and concealability. If you are looking for a fight, or know trouble is headed your way... get a long gun.
2) With regard to the military... you cannot compare our selection of caliber to LEOs and private citizens. The Hague Convention requires us to use FMJ ammo (except on certain terrorists) which has lousy results in any caliber. If you are restricted to FMJ ammo, then the bigger bullet is better IMO. This is why the DoD is returning to the 45ACP for all handguns. The RFP has already been released asking for entries.
3) With private citizens and LEOs, there is a great selection of hollowpoint/defensive ammo to choose from. With appropriate ammo, the 9mm is plenty potent. It earned its bad reputation from the early days in LE where 9mm HPs were still not at peak performance. While I do not feel less safe, or under-armed when carrying a 9mm (w/ appropriate ammo), I prefer the 45ACP. Why? Bcz with appropriate ammo it makes a bigger hole. In the end though, shot placement is key and it's a defensive tool, so it doesn't matter what caliber it is (unless you start talking mouse guns).
4) There are plenty of failures to stop in all handgun calibers. Heck, even in the 1920s, a Tommy Gun in 45ACP (read: higher velocity from the longer barrel). I want to say it was "Baby Face" something or other, but a gangster was in a shootout with a couple federal agents. He was hit 17 times (yes, seventeen) by the feds 45ACP Tommy Gun. He charged the two agents and killed them both, then drove off dying later of blood loss.
Banana, if you asked about this to buy your own gun, find the one you can most easily shoot well and practice with it. If you asked to stir the pot on an age-old debate, then congrats.