Stopping power and killing power are not the same thing. Almost any pistol cartridge has killing power. In fact, up until lately, since the inner cities have been overtaken with 9mm ammo flying hot and heavy every night, I would have said more people have been killed by .22s than all others combined when you take into consideration accidents, suicides, etc. It may not be true any more.
Stopping power is a different matter. When I used to read gun magazines, I think it was in one of Jeff Cooper's columns in which he answered a writer's question of what handgun to take to Alaska to stop a grizzly charge. He said there was no documented instance of anyone stopping a bear charge with a pistol and only a heavy rifle or shotgun with slugs would be up to that task. This has been years ago, so that may have changed with the advent of all these .50 BMG derringers and the like that are on the market now. Bears can and have been killed with far less (I have read that .222 Remington was the choice of Eskimos to hunt polar bears), but stopping them is another matter.
Energy figures are misleading. A .22-250 Remington has more energy than a .45-70--which would you rather have to use on a bear? Stopping power is more closely related to caliber and bullet weight. Velocity, after a point, only serves to flatten trajectory and make hitting things easier. A fellow named Taylor addressed this in early 1900's.
On topic, I have owned and used the following pistol calibers: .22LR, .32auto, .38 S&W, .38 S&W Special, .357 Mag, .44 Mag, .45 ACP, and .45 Long Colt. If number of rounds fired over the course of a lifetime is any indication of a 'favorite', then the .22 wins hands down.
I have only felt the need to carry a gun once in my life, and that was for about four hours. At the time the only handgun I owned was a Ruger Blackhawk in .45 LC so I stuck it in in the waistband of my pants, covered it up with a jacket, and walked through the Wichita Kansas airport. Imagine doing that today.
Today, if I felt the need to carry a gun where I was going, I think I'd just re-think the whole trip as to whether I really want to go at all. Getting in a shootout is about as low as anything can get on my priority list and I'm fully aware that a person often doesn't get to choose the time and place; it chooses him. That's a decision I've made--I'm not going to tote a gun around on the off chance that I will be in Luby's cafeteria when some lunatic opens up. I'm not saying it's right for everybody, only for me. Although I own a number of handguns, it is apparently not for protection as I keep them all locked up, unloaded.
So, for me, with the stopping power question rendered moot, the .22LR is the favorite cartridge.
