I live in black bear country, and they've been coming down into our subdivision (right by the mountain in Albuquerque) for the last couple of weeks. (Lots of "Missing Cat" and "Lost Samoyed" signs on the lightposts, BTW.) Anyway, when I hike back in the hills I feel totally happy with my Glock 33 in .357 Sig - black bears are basically giant raccoons that don't want to bother anyone. If one got crazy, I think 10 rounds would change it's mind, and there's nine more where that came from in my other pocket. I suppose I'd be better off with my Ruger .41 mag. Blackhawk, but it seems like a lot to schlep.
Grizzly country? 12-ga. pump with slugs. Seriously, though, you can usually avoid an attack (there's lots of info out there on how). Even in the part of Glacier where they warehouse the "bad bears", they're training the things to avoid people. If a "bad bear" goes recidivist and comes near people, the staff lock it up in a cage and harass it for a couple of days - the bear associates people with being harassed and begins to avoid them.
But, if I *were* attacked by a griz, I'd be with denfoote. I've carried my .41 in griz country before, and haven't felt too secure about it. When I had the Mossberg pump with the slugs, I felt secure. That's a lot of lead.