The Black Bear exhibit is considerably smaller. About 1 acre in size. I don't believe they have any plans to aquire and exhibit Polar Bears. The Alaska Zoo, a few miles up the road, exhibits 2 Polar, 2 Black, and 3 Brown Bears. The Alaska Zoo is currently also in the midst of a major expansion of their Polar Bear exhibit. Taken together, these to facilities have quite a nice collection.
I hope you do get the chance to visit Alaska. I'd recommend focusing on the axis of Denali to Seward and Valdez to Homer. Anchorage sits right in the intersection. In truth even a visit that limits you to Anchorage and the Kenai Peninsula is well worth the trip.
