The way I see it is simple. I can carry 23 rounds of 9mm without a spare mag in a full size Glock 17 with extended mags, and easily conceal it. A 1911 is more comfortable to carry, but if I’ve learned anything in life it’s that our bodies don’t hold up like we’d like them to, and I’d like to be able to still shoot when I’m old.
Also, many of the places I’ve lived, even with spare mags, single stack 45’s are slower to shoot and I would have to reload sooner. If you’ve ever lived in an area dominated by gang activity, you know what I’m talking about. Split times can actually be a real world problem. Thankfully, I now live somewhere I can carry a wheel gun and not feel like I need more ammo. Back in Phoenix or Houston, I had as much ammo on me as practical and came too close to needing it more times than I want to think about. That’s why I live in the woods now. MM, MS13, etc don’t typically travel alone, something to bear in mind. I’m sure many here are acutely aware of all that, but it’s worth mentioning for those who haven’t had the opportunity to live in places where their presence is a fact of everyday life.
If you need the extra capacity, and need to shoot faster, 9mm wins. If you want to keep your body capable of shooting well into old age, 9mm wins again. Like many previous posters have mentioned, current projo and powder technology has made the 9mm a new animal, and the testing and results are easily available for anyone to see for themselves. DocGKR has posted quite a bit about it on LF.
Also, it’s important to think about where you’re going to be. A 45 or a 9mm is fine in society, however...
If there’s ANY chance of a fucking bear, 9mm is better than rocks, but it’s not enough, and neither is 45. That’s why I have a big bore revolver. People will just shoot or stab you, or beat you to death, or some shit like that, worst case. A bear is gonna fucking eat your ass alive, or at the very least permanently maim you, if it decides to attack you. Just felt the need to drive that point home. Don’t carry anything pleasant to shoot in bear country, I don’t care what time of year it is or if you’ve seen one before. My buddy in Oklahoma had a black bear walk through their yard, in town, just randomly. You can’t predict their behavior, where they’re going to be, or how they’ll react to your presence, and if you need to put them down, it needs to have a real chance of killing the animal or stopping its advance. Even a juvenile black bear can kill a grown ass man if it believes in itself.
Just my 2¢, of course.