I hate to sound heretic, but it's not the size of the caliber, but the fun of shooting of the caliber. The more fun it is, the more you shoot. The more you shoot, the more likely you are to train. The more likely you are to train, the more likely you're going to put your bullets in the boiler plant for immediate cessation of violence.
This is why the wonderfully accurate and ergonomic 1911 ends up proving such a fight-stopper. Not because it's bullet, at the magical twice the weight of one thousandth of an adult human's mass, has awesome power. If that were the case, .44 Magnums would have a better track record. The .45 ACP and the 1911 just combine to easy shooting (low bore axis, light trigger, proper grip angle), and fun shooting (it makes the big boomie sounds, and it feels manly).
That's just my theory.