Polar bear vs. orca

"The icy cold Arctic is home to both the powerful polar bear and intelligent orca, two mighty predators. But which animal is the fiercest of the ecosystem? Does the polar bear's patience in stalking its prey and strength in attack put it on top? Or does the orca's ability to work in a pod give it the edge? Compare and contrast each animal's features and skills before you declare the winning predator"--Provided by publisher.