Personally I've never cared all that much about the caliber, within reason. To me it has always been more about having a reliable defensive weapon that I could use quickly and accurately. If the situation meant that was a 380 then I had a 380, it was better than my hands. If the situation allowed a full size 1911 and two spare mags then that's probably what I carried. I consider my staggered magazine 9's to be harder to carry than the 1911 and despite the theoretical recoil differences I'm faster and more accurate with the full size 1911 than any other handgun I own. It's nothing magical, just the best setup for my body mechanics.
Honestly, if we were JUST talking about self defense and enjoyment didn't factor in, I'd go with a Sig P226 in 357 Sig. Lots of rounds, top of class stopping power and most importantly of all, my first round on target with one is about as fast as my 1911 and even with the crazy recoil impulse of the 357Sig I can get the second round on target about as fast as well. Ergonomically the gun works well for me in almost every way, except the one that drives me nuts. The back of Sig's grip, right below the slide, bites the HELL out of my thumb knuckle during recoil if I'm holding it properly for shooting. I mean, marked after round one, bruised after two, bloody after a magazine's worth when shooting 357 Sig. I can go a little longer with 9mm, but it's not pleasant.
Let's face it, pretty much EVERY other factor involved in a self defense shooting will play a bigger role than the caliber once you get to 9mm and don't get crazy. Obviously if you start comparing 9mm with some of the super heavy rounds it's like comparing most pistols to a pistol caliber carbine, not fair to the handgun. Realistically, shot placement, multiple rapid hits, situational awareness, keeping or creating distance.... these are what decide who goes home and who goes to the morgue. Get the first hit in, get it somewhere important and then do it again. Rinse and repeat until there are no more threats. The drill doesn't change whether it's 9mm or 454 Casull. Ok, maybe I might stick with one center of mass hit with the 454.