The most obvious feature difference is the browsable API.

Flask API also shares the same architecture as the core of Django REST framework, which I think just has a really nice separation of concerns.

Also the interface of `request.data` means is easy to transparently support both JSON and form requests, and the nice content negotiation on responses means it's easy to build services that power both an HTML front-end and an API from the same endpoints.

Right now Flask RESTful is more mature of course, but I've got high hopes for this, and it's been super fun to build so far.