+1 on the .357 mag for another reason -- the noise. That sharp concussion of the .357 magnum from the business end is considerable. And unpleasant inside of 20 yards. Even if you miss, that blast may change a bruin's mind about seein' what you taste like.
If I was stuck deciding between .45 and .40 for black bear, I'd look for the hottest 180gr FMJ .40 load I could find. I want something that will penetrate and break bones vs. expansion. Browns and Grizzlies are much tougher critters and I'd opt for any Elk-suitable rifle over a handgun.
the only time I would even enterain whackin a bear in the nose is if it was AFTER I had put all my lead into him and it was a test to make sure the beast was dead...and even then it would have to be a really big stick.
We have some crazy folks here in California (is that a surprise?
) who use pointy sticks to hunt bear. It's amazing to watch a pair stalk within range like a Marine sniper to get their shot at 40 yards or so. Even with a compound bow, bears seldom fall right away.