Actually the Oppo ignores Cinavia watermarks in MKV and M2TS files, as do a number of other BD players.
One really shouldn't compare a full featured media box to a BD player. The Oppo is a simple renderer with SMB access to shared files. A media box offers considerably more functionality such as file management and storage, additional file sorting options, etc. The Oppo does a lot, probably more than any other BD player, but its not a media box. If your stated purpose is only to watch media files, there are less expensive options with more functionality.