What is the benefit of using Spring REST Docs comparing to Swagger

I just saw a presentation here that touches on your question among other topics:

Swagger doesn’t support hypermedia at all / it’s URI centric
Swagger’s method of inspecting your code can lag behind your code. It’s possible make a change in your code that Swagger fails to understand and won’t process properly until Swagger gets updated.
Swagger requires lot of annotation, and it’s painful to include the descriptive text you want in an api document in annotations.
There are just some things that Swagger can’t figure out from inspecting your code.

In any case, these are just a couple of points. The presenter does a much better job discussing it than I could.