This is the best write-up I have seen on bear protection handguns.
https://alaskagunsite.wordpress.com/2017/01/01/the-case-for-the-357-magnum/
In my eyes, a bear defense handgun needs to be absolutely reliable. If you stuff an auto in a bears mouth, or against anything while it's attacking it likely will go out of battery and not go bang. If any type of failure happens, clearing said failure is really tough one handed especially with a bear on top of you. Just pull the trigger again in a double action revolver. It needs to penetrate, not expand and that means like 4+ feet to get to something in the CNS that will shut things down.
I have a 44 mag 629 S&W Magna Classic that I love and carries great in a Kenai chest holster like previously mentioned. But for last ditch and always there I have a 3" Model 65 K frame loaded with Buffalo Bore 180 hard cast LFN ~ 1300 fps.
I love my auto handguns for most everything else but for this one the double action revolver is the better tool IMO.