Hippo
Hippo wins: wider angle when jaws open, stronger bite, doesn't lose the size battle, thicker hide.
Hippo also has better terrain versatility. It can do equal damage whether the fight is on land, above the water's surface, or under water.
In short, Hippo offense & defense >>>> Bear offense & defense.
Edit: OP you should also specify the type of bear, because a black bear or panda don't need to be anywhere near this rumble
