While I agree that any service caliber cartridge, 9mm up to .45 and everything higher powered or in between those two diameters, is generally suitable for SD/Duty and is generally a compromise of all factors, being able to put suitable rounds on the threat takes so many paths. Shootability, accuracy, ergonomics, sighting system, load are some of those factors that need to be considered.
Some people look at gel tests as the deciding factor, some only at actual shootings, some only at live tests (rare and expensive). I look at all of them and at some level I have participated in all of them. Shooting pigs with medics who jump in and try to "save" them is eye opening for sure. Shooting 100s of head of big game including cull deer and hogs. Going to a meat processing plant and shooting a few hundred animals in the head with a variety of calibers. I even got to shoot a Deer with a bullet proof vest on.
Can you kill a Deer with a .223? Yes, but you better be using a good bullet and place it properly or you won't fill the tag. I've seen all manner of craziness shooting gel, covered gel, contained gel, live animals, Fackler boxes, etc. Gel is just a comparative test medium that offers consistency. But it does NOT represent the structure of a living, breathing person. The human body has bones, connective tissue, and soft tissue of fairly different densities. A fatal shot one day may not be a fatal shot the next day placed in a similar place. Also recognize that fatal, and incapacitated are NOT the same thing. I was the first ballistics expert in the US to use energy thresholds, mass equivalent coefficients of restitution, equations of motion in viscous media alongside virtual autopsy to prove entrance velocity of a projectile into a human.
"We" make too much of the caliber wars. Pick one, practice, be efficient and set metrics. But taken too far, folks really WANT to believe that a .380 is as good as a 9mm, which is as good as a .357 Sig, which is as good as a 10mm. But that is not true either.
If you can shoot and carry a full size, double stack 10mm with a light, laser and an Optic...WELL, then do so. Most can't for a variety of reasons, so they take some sort of path, paved with good and bad opinions, good and bad data and make their choices. And, absolutely, without question, the better a shooter, and the better you handle stress, the less "sufficient" a firearm/caliber you can carry. Another huge factor lost on most. I will routinely outshoot novice shooters on any drill with a 10mm or +P 45 and them using a full size with bunny fart 9mm loads. I have a LOT more choices that are "sufficient" than the vast majority of the average person who has a permit and a pistol and never practices.
In my defense pistol rotation, I have a few micro-9s. But I prefer a full-size 9mm to those. I prefer my compact .40s and 45s to that. I do have a 3" Kimber .45, loaded with +P 200 grain ammo in the rotation. I shoot it well, and I am accurate with it.
SO, my thoughts...a more powerful cartridge is always better IF you practice with it and can shoot it well. If you don't, then no, the 1911 platform and the .45ACP is not a good choice for a novice.
There is a monthly challenge here on GT that you can start out with. If you look at post #12, you will note that I was faster with a .40 and a .45 than I was with the CZP07 9mm.
https://www.glocktalk.com/threads/december-challenge.1992063/#post-32376812
But regular training is so much more important than the platform or caliber or sighting system. Training, on a regular basis is a hard thing to argue against, so we don't see a lot of GT traffic on it. While I believe the GT membership represents a higher than average incidence of folks who are proficient and compete, fact is, the average GT member is lacking as well. Since I was in my 20s, I have "hated average". Average sucks! The only time average did not suck was when I was still green in shooting 3Gun and I finished exactly in the middle, and won a Firebird rifle.

But you need to be much better than average when it comes to defensive pistol issues.