As I read through this thread I kept going back to thinking about boxing. I see the Gorilla punching and beating the bear for a short time, getting worn out due to the carnivore/herbivore argument presented, then the bear going to town. My vote is polar bear.
Besides while everyone's thinking that the gorilla might be using weapons with his opposable thumbs, let's not forget that polar bears are hopped up on caffeine from Coca-Cola, not to mention they have the ability to touch the sun.