Swagger seems to have more awareness and adoption but we have fully embraced RAML due to its "composability" features which eliminate much of the boilerplate and copy/paste/tweak required by Swagger. Making the API spec easier to author & maintain is well worth the downsides of not being able to tap into the Swagger ecosystem. If we really needed something from the Swagger ecosystem, I don't think it would be difficult to create a RAML->Swagger converter. There is already a converter that goes the other direction.

But whichever one you choose, this stuff is awesome. We author API specs and then codegen mock services, client side wrappers (Angular services or Backbone models/collections), server side DTOs and controllers, and pretty documentation. Having that all done from a single authoritative text file under source control has drastically reduced the friction between frontend and backend developers.