Who Would Win in a Fight Between a Bear & a Gorilla?

IMPORTANT: We're talking about a silverback gorilla and a grizzly bear, here. Alpha males, the both of 'em. Bears have claws. Gorillas have opposable thumbs. Bears weigh a lot more. Gorillas are much more agile. Bears have razor sharp teeth. Gorillas have razor sharp brains. Hold on to your seats ladies and gents, this is gonna be a close one.