Thinking about this more. Have not been to Franklin Park in 10 years likely, when I wen't in the middle of a massive snowstorm. Definitely my most memorable zoo visit ever, barely being able to traverse the pathways. Have been to Boston since but did not have time to do the zoo as the aquarium is obviously more centrally located. But Roger Williams and Franklin Park are the larger zoos I have been to in the region. Roger Williams is a really nice zoo, yet its collection is largely standard, not many rareties when I thought about. Franklin park currently has kea, stellar's-sea eagle, siberian crane (as well as 4 other species of crane), kiwi, potto, Ruwenzori Fruit Bat, and red-breasted merganser. Now I am not saying Franklin Park is better, as it is obviously not, yet it does have some very nice-rare species. Plus is doing some great conservation work at the moment. Especially with the aquisition of "Grassroots Wildlife Conservation", which works to protect endangered New England species.
Now if only Franklin Park get some investment, although I am happy to see their financials stabilize after years under the threat of closure. An outdoor gorilla exhibit (something simple like a netted habitat would work great), bringing in another megafauna species (bears maybe), and renovating the bird house are all things I would like to see done.
NE Zoos I have been to:
1. Roger Williams
2. Franklin Park
3. Beardsley
And aquariums for fun:
1. Mystic Aquarium
2. NE Aquarium
3. Maritime Aquarium