All depends on the build and play style. Before FB, very few (if any) pure birds exsisted. Warbirds, Copper bears, and Shivering xbow bears always stood out as having the best "chance" when I played that level.

Personally, I did best using my Copper bear (but that is because I was never a "range" player.) I saw multiple Shivering bears who maximized their range and owned mages. If it weren't for the attitudes at the 30-35 pvp level, it would have been my favorite.