Beets is fantastic and I have only begun to test it on my collection. I think I have read nearly all the documentation but cannot see if there is a way in the config file to tell it to search discogs before musicbrainz, or to only search discogs.
My preference for discogs is because I have contributed a lot of information to the database and know all the data for my CD rips to be accurate on there. I have also found adding the discogs ID for releases not found immediately has been the best way to get the job done.
Thanks for Beets.