I know that a 45 ACP is better then a 38, no doubt about it, If I knew I was gonna need it, I'm pack a 1911 (or better yet a rifle). But I dont know that. Chances are I'll go the rest of my life without needing to defend myself. Don't mean I'll wont carry. JUST IN CASE.
BUT COMMON SENSE PREVAILED.
I found I often left my 1911 in the truck or at home. A light pistol in the pocket beats a heavy pistol in the truck every time.
I'll stick to my 642 which is ALWAYS in my pocket. Dont have to worry about grabbing my gun when I leave the house, Dont have to worry about wheather its concealed or not, IF anyone knows. Heck most of the time I forget that its in my pocket.
My dad likes to say the .45 is pre-expanded. No dependance on expansion is a big plus to my mind. The 9 mm busts light cover (e.g., the old helmet penetration tests) and pops tires better. Though loaded to the same energy, the .45's greater momentum lets it penetrate a gelatin medium further when he bullets being compared have the same nose design.
Modern 9 mm is better than what was available back when the FBI was studying the issue. The Miami shootout was a big eye-opener for the ammunition industry and they acted on it, learning to make rounds that both expand and penetrate, where previously you had to choose one or the other. Nonetheless, I am slightly acquainted with one fellow who was shot through the thigh with one of the improved modern 9's (Federal Hydra-Shok) and it exited without expanding. So they haven't solved the problems to the point of being a guarantee.
Martin Fackler pointed out that, at autopsy, pathologists are typically unable to discern a handgun bullet hole made by a solid from one made by a hollow point. That's not true of heavy magnums loads, and is certainly not true at high power hunting rifle velocities. But among the more common defensive round power levels, apparently hydrodynamic temporary cavities are usually just that; temporary. So, if you get a gremlin hopped up on something that lets him feel no pain, or even, as in the FBI shootout, just on a lot of fight or flight adrenaline, hydrodynamic shock in this power range can turn out to be of no more than theoretical value. I don't know how you go about studying how often temporary cavity pain actually shortens stop time over what a solid would achieve? You kind of just have to go by subjective impressions of those who've seen both in action.
Jeff Cooper became a fan of the truncated cone bullet design by the end of his life. Reports had come in from his contacts that they were stopping faster than hardball. The flat meplat makes a temporary cavity (which might answer my previous question) but it also does crushing damage as compared to a round nose. It would be interesting to learn whether that crushing damage has more shock effect on nerves than temporary cavities do? I don't know how to study that conveniently, either?
In any event, between expansion reliability issues and hydrodynamic shock impressing gremlins unreliably, I long ago decided to opt out of the expanding bullet argument altogether. Blunt solid projectiles in .45 ACP or in .44 Special for my 3" Charter Bulldog (when I need smaller size and weight) are my personal preference. But I do enjoy experimenting with both smaller and larger rounds to see what they can be got to do?