My personal gun of choice is a Glock 23 with Corbon or Federal loads. Compact, simple, and reliable.
I'm not very picky about my gun or my load. As long as both are reliable, that's good enough for me. I am a firm believer in training over technology.
I don't care about the caliber, either, although I'd prefer something over 9mm. However, if I have a .32, and I have to shoot someone, I'll use it. I will shoot him, and then shoot him again. I will continue shooting him until he is laying dead on the ground or I am out of bullets. If I run out of bullets, and if he hasn't killed me yet, I will reload and shoot him some more. I will use the tool that I have, not stand there and say, "gee, I wish I had my 9mm (or .45, or .357).
Watching people rehash the same old caliber wars has become an amusing sport to me. I wouldn't carry a 9mm by choice, but I sure as hell don't want to be hit with one.
There are 3 things that are the most important to me:
1) Training
2) Training
3) Training
Oh, and training is important, too. I think that training with what you carry is important, but fundamentals are key.