Hello Udo, the difference is obviously in the reception of the traffic data. I had chosen the MT-D because it receives the traffic data directly via DAB+. The MT-S also needs a smartphone with the Garmin Drive app installed to receive the traffic data. Personally: the diversions recommendations displayed by the device saved me about an hour of traffic jams/stop and go in Germany on Sunday afternoon. When I heard the traffic news with the closed A61 on the car radio, I was already on the diversions route via A4, A555 and 565 thanks to Garmin.