Big difference is it's implemented in pl/pgsql so as Aquameta evolves, there's no external deps. There's a function called endpoint.request(http_verb, URL, post vars) and then it does the rest in plpgsql. A thin Go daemon just takes the request and throws it at the function.
It does a lot of the same stuff PostgREST does. Automatic REST interface to any database, but it also hosts static resources, and dynamic mapping of URL templates to functions.
Needs a rewrite though. That's probably the next big dev push. Right now we're rewriting the system catalog (meta) and the data VCS.