Well Philly is much larger than Central Park Zoo and has a significantly larger species list so I wouldn't say that's an apples to apples comparison either.
I think Philly is a solid zoo. Big Cat Falls and Carnivore Kingdom are both quite good and the McNeil Avian Center is one of my favorite exhibits anywhere in terms of entertainment value. You can check out my review of that exhibit on the forum if you like.
Treetop trails is a nice new feature. Otherwise, there is a very nice and large hoofstock/crane/stork exhibit, a good bear section, nice cheetah and wild dog exhibits side by side, and lots of buildings with impressive species mostly in so so or worse exhibits. Oh and this is the best zoo I have been to for viewing aardvarks, which is a nice plus for me.
I would also say that some exhibits are quite as bad as some on here think. The orangutan exhibit for one, which has 3 large trees that they can climb.
