I just stumbled across some interesting information. I have been using the Pronto CCF files almost exclusively because the Universal Browser function allows you to drag & drop individual commands into the MX-700. With an MX-700 MXD file, you must import the entire device to get at the commands.
Mike from SRC just posted this nugget at Remote Central - Universal Browser will also open MXD files and allow you to drag & drop individual commands, just like the CCF files. I tried it and it works. This is great news since it opens up another avenue to get at individual and/or discrete codes.