It's interesting to see no one has pointed out the difference between merely killing a bear with whatever round is chosen vs stopping a deadly attack. A .357 will kill a bear, but will it stop one during an attack as quickly as something like a .454? A few extra seconds of life in the bear could be the difference between life and death for the defender. Granted, shot placement with either is the really critical factor, something hard to do during the heat of the moment, but I'd think if both could be shot well the harder hitting round would stop an attack sooner. YMMV.