Polar Bear Cub = Cute Polar Bear = Fluffy coca-cola drinking friend Hungry Polar Bear = Ruthless Killing Machine.
If environment didn't play a factor, I think the Polar bear would win. Why? No reason really, just polar bears are badasses.
Polar Bear's are bigger than Grizzly Bear's too so that's a major advantage. /thread hijack complete Edit : But there's some Grizzly's you do not ------ with http://rbenson.wordpress.com/2005/09/16/worlds-largest-bear/ "Based on the contents of the bears stomach, the Fish and Wildlife Commission established the bear had killed at least two humans in the past 72 hours including a missing hiker."