The stand-alone will probably cost about $1K more, since it will have accelerometers and air-data sensors so it can, well, stand alone (fly the plane with no input from the EFIS). The Dynon autopilot will ?steal? this data from the efis. If you only fly vfr, I think you should save the money and just buy the Dynon servos. If you fly IFR, then give serious thought to redundancy questions. e.g., I have the Trio Pro (IMHO a great autopilot), plus attitude data from a pair of GRT HX?s and a Dynon D6. If both HX?s and the D6 go belly up, the Trio will still fly the airplane and, if my gps is still working, shoot an LPV approach right down to the runway.