Shot placement, speed and situational awareness trump caliber every time.

With that said, typical defensive loads for humans are not appropriate, as they're designed to expand and limit over-penetration. Bears have much better natural armor than humans, so a large jacketed (JSP better than FMJ) or hard-cast lead bullet is better to achieve enough penetration.

The prevailing wisdom seems to be that a .357 Magnum loaded with heavy JSPs would require precision hits on the central nervous system to reliably stop a bear. Under stress, few people can make precision CNS hits on a charging bear with a handgun. As a master-class competition handgun shooter, I would be doubtful of my ability to make such a shot.

A .44 Magnum or .454 Casull is more appropriate -- for those that can accept the weight and are capable or shooting them effectively. I'd rather have a shotgun loaded with slugs.

It's worth repeating that your best move is to avoid confrontations with bears. It's also worth repeating that you shouldn't carry firearms anywhere unless it's legal to do so and you are trained to use them safely and accurately.