"Incapacitation" occurs because:
Pain from being shot
Fear/shock from being shot
CNS disruption
Blood loss
None of these, except the CNS shot, has the ability to immediately stop-though all of them MAY stop.
Relying on blood loss takes time-minutes. If you have to shoot some one, you don't want to wait MINUTES before they cease hostilities.
The difference in the size of the wound, discounting bullet expansion, between a .25 and a .45 is only 1/10 of an inch-not a lot of difference.
The sight of a gun ceases most hostilities. Shooting someone usually ceases most hostilities from pain/fear/shock. If shooting someone does not stop him by the previously mentioned factors, you have to wait on blood loss. That's a LONG time-especially if they are trying to do you harm.
So-my theory is this: Carry a gun. Any gun. If you have to use it, TRY for a CNS shot(s). If you go about your day in a normal fashion, odds are you won't need your gun. If you are doing work that requires you to put yourself in harm's way-carry the biggest gun you comfortably can. Bigger is better-but not much better.
I do not count on sight of a gun ceasing hostile action.
"Someone usually" is a generalization that could be hazardous to rely on.
I have not "needed" a gun in over 25 years of carrying, ever, including when I was a cop
What if "harms way" comes to you, regardless of occupation?
I don't understand minimal caliber advocacy when so many small firearms are available in 9mm or better, but what you prefer (rationalize) doesn't affect me.
I prefer to bet my life on larger / more powerful bullets and my preference is based on what I've seen firsthand.
Between myself, my wife and my kids I've field dressed 40+ deer - over 30 were killed by me; couple dozen bowkills, muzzleloader, rifle, and even 10mm pistol, nearly all the deer were inside 20 yards and double lung hit (bait and its legal) .
It is an accurate generalization
(exceptions of course) to say that given a double lung hit there is an observed positive correlation between size of wound, blood on ground and decreased distance traveled.
Would I prefer a smaller hole in a deer? No.
Would I prefer smaller hole(s) in someone trying to club, slash, stab, shoot me? Absolutely not.