I would use FTR, and add both argus and mepo tv-server to FTR, then you have best of all worlds. Run the HD-PVR on mepo server and rest on argus.
imo FTR is the more complete backend solution, excellent sceduling options, and several clients (web, imbot, ios, android, xbmc, mepo...)
Also, I don't know this for a fact, but I believe the FTR api is superior, and has potential to be a great xbmc backend, if the xbmc developers take advantage of all the posibilites. Stuff like Channel logo's automatically read from backend is so cool, I import channel logo into FTR and all my clients automatically have them, I was so surprised when I fire opp xbmc and all the channels had logo's
Fred has promised some cool stuff for FTR users in the future, you know if you start watching a recording on one client and stop it, you can continue from same spot on a different client.
also, true timeshifting is comming soon, it's the only thing I really miss in the XBMC frontend (other shortcommings I can live with for now).