This topic has been argued about for years and it will continue to be argued over for a long time to come... Just like arrow selection, everyone seems to have an opinion about what is best, but what really matters is, "Can you hit your target when and where it counts?"
I'm required to carry a 12 ga. or a .375 everyday of the summer for work. I like 1 3/8 ounce black magic slugs from the pump, but I prefer the rifle.
But I don't want to post anything about guns and bears without this warning:
While firearms definitely have their place in grizzly bear country, don't let the false security of a firearm change your behavior! It is easy to say, but hard to do. I constantly find myself moving with less purpose and being less observant when carrying a gun.
Not only that, but bears, and especially black bears, bluff (including bluff charge) a lot. Sure "shooting first and asking questions later" is usually the best way to go if a bear is within 10 yards and closing the distance, but avoiding the charge in the first place shows the most respect for the animal, for bowhunting, and for oneself.
That and don't be "bearanoid." If you are expecting to be charged, something is wrong with the way you view bears, or with the bear-human relationship in your hunting area.
The scenario painted by the original poster (bears regularly charging boats and people) suggests that the outfitter in the area is mismanaging his clients/guides and/or his waste/baiting stations. Frequent and regular bear attacks are not normal and are highly undesirable. I would find a new place to hunt because something is wrong at that camp.