I can't speak on the Pittsburgh Zoo as I've been, but I can speak about the others as I've visited them many times! To be quite honest, it all really depends on what you want to see.
The Wilds - The Wilds is a 10,000 acre conservation center in eastern Ohio that specializes in ungulates and medium-sized carnivores. You drive through the huge paddocks in open-air safari vehicles or tour buses which do stop to allow for the viewing a photographing of animals. They also make stops at several small stations where you can get off and walk around including a Medium-Sized Carnivore Center where they manage Cheetahs, African Wild Dogs, and Dholes. Other animals you would see on your tour include Przewalski's Horses, Persian Onagers, Bactrian Deer, Burmese Brow-antlered Deer, Indo-chinese Sika Deer, Fringe-eared Oryx, Sichuan Takin, Grevy's Zebra, Indian Rhinos, Southern White Rhinos, and three sub-species of giraffe. If you want a peaceful day in beautiful setting and are interested in ungulates, you should visit The Wilds.
Columbus Zoo- By far the best zoo out of the bunch with new exhibits opening every few years. The newest of which is Polar Frontier which features exhibits for Polar Bears and Kodiak Brown Bears and Arctic Foxes. For the most part of all of the exhibits at the Columbus Zoo are very nice, but there are a few that aren't as good as they could be. Some of the exhibits in North America and The Shores are beginning to show their age and, of course, there is the famous Sumatran Orangutan exhibit in The Islands of Southeast Asia. The Columbus Zoo is another zoo with several rarely exhibited species including the Alaskan Moose, Wolverine, Florida Manatee, Tiger Quoll, Banded Palm Civet, Brush-tailed Bettong, North Island Brown Kiwi, Queensland Koala, and Black Duiker.
Cincinnati Zoo- If you like zoo history, the Cincinnati Zoo is a great zoo to visit with all of the historical buildings and history in general. The Cincinnati Zoo does have some exhibits that are in need of a renovation. The Spectacled and American Black Bear grottos are both original Hagenbeck designs with little natural substrate. The exhibits in the Reptile House can also be small for some of their inhabitants. However, the Cincinnati Zoo does have some very nice exhibits including Jungle Trails and the Insect House, and they have an amazing avian collection in the Wings of The World building. There is of course the new Night Hunters exhibit and the new giraffe calf. The Cincinnati Zoo is probably one of the best zoos for rare species with their Sumatran Rhinoceroses, Aardwolves, Aye-ayes, Banded Palm Civets, Gray's Crowned Guenons, and Gray Bamboo Lemurs just to name a few. The Cincinnati Zoo is also constantly improving and those sad exhibits are disappearing or being renovated and expanded quickly. I would rank Cincinnati second after Columbus out of those zoos.
Cleveland Zoo- The Cleveland Zoo is absolutely huge and getting from one place to another is a trek to say the least. The Primates, Cats, and Aquarium building, which is absolutely terrible anyways, sets way off from the rest of the zoo, and on a hot day it can be quite a feat. Unfortunately, a lot of the zoo's rarer species are in that building. I find the zoo kind of lackluster when I went a few years back. Besides Wolf Wilderness, the entire Northern Trek section is very disappointing with grotto after grotto and bare paddock after bare paddock. The grottos are larger than some, but they're still grottos. The African Savannah was rather average with large fenced paddocks for the ungulates, a grotto for lions, an old Persian Leopard cage, and an old monkey island for Colobuses, Klipspringers, and Rock Hyraxes. However, the Black Rhino yard is rather nice, and is quite successful. The Australian Adventure is rather nice, but has a very childish design. The Rainforest is also nice, but since it is indoors some of the exhibits are too small for their inhabitants or do not offer what other exhibits for the same species do, like the famous orangutan exhibit. Overall, the Cleveland Zoo has a nice collection with the largest collection of bears in North America with every species except the Asiatic Black Bear and the Giant Panda, and countless primates, with some nice exhibits, but a lot of it’s rather outdated. However, African Elephant Crossing opened this year, and that is worth seeing.
If I had to cut a zoo from the trip, I would personally cut the Pittsburgh Zoo as it doesn't seem to be as large or as diverse (Having never been I can't speak on true quality) as the Ohio zoos. Not to mention that The Wilds is an amazing place, and even though it doesn't have the same number of animals, it is an amazing experience.
They're all rather nice zoos, but it depends on what you want to see. I hope that helped!
