I'm a (Internet) genius and here's what I've learned in my extensive (Internet) research:
There is a fallacy in handgun caliber considerations that suggests different loads have better or worse "knockdown" power. Rifles are for knockdown, not pistols. Most Pistols (.460 & .500 notwithstanding) lack the kinetic energy to create hydrostatic shock that's sufficient to damage elastic tissue. However PENETRATION, not just of flesh and bone, should be a consideration.
Scenario: You're in your vehicle with the doors locked and a maniac is trying to force his way in. Are you going to roll down the window to shoot or carry a caliber and bullet that will retain mass and energy after passing through tempered auto glass? What if you shoot through the door instead of the window? What if he's wearing a heavy down coat?
Scenario 2: maniac is charging down the hallway at you, you unload on him. Some rounds hit their target, others miss. Are those misses going to penetrate a few layers of Sheetrock and harm the family next door?
Any handgun that you will actually carry is a good choice.
