DMU, Temple, AZPod and Scholl are usually among the top on people's lists though the top 4 spots are arguable. The other 4 schools are usually listed in the 5-8 slots, but again which one belongs in which slot is arguable.
I've never seen any kind of official survey of any kind. It's mostly just individual preference/attitudes, but the lists almost always work out as above.
Good pods come out of all of the schools, and all of the schools also produce some not so good pods.