Even though bears are really, really big, I dont think the have the physical strength to stop a gorilla from pounding them into a rug. Figure how much of the bear is muscle compared to how much of the gorilla is muscle per capita. And Grizzly Bears at the most get 850lbs while gorillas can get to be about 600lbs, while not even, it really closes the gap. Couple that with the difference in muscle and I'm going with the gorilla.
On second thought bears kick ass