I love the Ruger SP101 .357. To me, it feels perfect in the hand and it's foolproof. And, it is so much easier to clean a revolver.
I voted .45, but it depends on what "bet your life" means. You're in a gunfight with someone? Or.. you can only pick one caliber for all around? or.. you need best performance for home protection? or.. you need it to be reliable but don't expect to use it? I'm always surprised how many people love or hate specific calibers. It seems to me the specific situation would have so much more to do with what is best than there being one caliber that is best. Anyway, the .45 is tried and true... but in retrospect it was a toss up between that and the .40. The .40 is considered to be superior by many people who know what they are talking about. 10mm too. I love .357 but I hate revolvers, so.... the other nice thing about .40 is the MP5/40. Friend has one.... it is jizzy.
Most of the handgun rounds I fire are 9mm, followed by 22LR. I also like shooting the 38/357 revolver. But betting my life? My trusty Glock 22 in 40cal.
.357 mag with the right round is a pretty good show stopper. Everything is relative, though. I read a pretty good stack of documents about a belligerent non drugged up yet very combative Samoan that took THREE .357 rounds to the chest, afterward, he knelt down on one knee and said, "That hurt." I gather he's out of prison and now picks grapes somewhere in California.
The loads for most calibers are so well sorted out by now that there isn't going to be a huge divergence in efficacy between them. 10 years ago, sure, but not now. If your ass gets hit with most anything in the poll, your ass is near as makes difference, dead. If not, a second round is coming your way to close the deal. Far far beyond that is how well one can handle a gun in stressful situations; can you shoot accurately with it to begin with? Can you shoot with it accurately under strain? Can you dearm the gun when the situation returns to normal?
Even a cannon is useless if you miss the target. Back in the '80s, the 9mm para was in its heyday, because they could make lightweight rounds that wouldn't penetrate deeply enough to hit major organs. They had a very high survivability rate, and a good "stopping" rate. But then the got a bad rap from the FBI trying to shoot through a car with them. Maybe they've changed the charge loading over the years, but from the early reports, 10mm was the ideal round if you wanted to shoot two perps with one bullet ... and you could get them to line up. I voted 9mm, but I'm a city boy --- I don't need a 30 mile lethal range. And someone in a car, running away, isn't somebody I'd need to shoot at. (The FBI were trying to stop known felons.) But then, if I wanted to intimidate, in the hopes that I wouldn't have to shoot, I'd go .45 ACP --- looking down the barrel of a 1911 feels like poking a stick into a bear's cave.
I've got a 9mm for the following reasons: 1. Cheaper to practice. I'm a cheap bastard at heart and the more expensive the ammo, the less frequently I'll practice. It doesn't matter what you have if you don't hit your target. 2. Small hands. I'm a fairly big guy, but have small hands. I have not yet found a .45 that fits my hand well. 3. Small wife. I want her to be able to use the gun if she has to. 4. 19 round capacity. Gotta love it. So I trust my life to an XDm9 with 147gr HSTs.