No framework at all. We use PostgreSQL and simply point postgREST at it, and it automatically generates an entire REST API from the database. Authentication and permissions are handled at the database level.
I can't think of any framework that would be more productive. Not having to maintain any back-end code is pretty amazing!
It comes with alot of nice to haves out of the box (auth, an admin backend, browsable api...) . Built on top of Django of course so there's some overhead there.
I wouldn't use it if high performance is top priority above all else.
Also +1 Django REST Framework, it's been a huge productivity boost for us. For a small team dealing with a large codebase, its high-level abstractions provide lot of consistency while also providing enough flexibility for more specific use cases.
I can't think of any framework that would be more productive. Not having to maintain any back-end code is pretty amazing!