Bus vs train

There is only the Romantic Road coach, but they make only one trip per day, straight through from Füssen to Rothenburg (in over 7½ hrs) with hardly a potty stop (for €72 pP).

The Romantic Road is some sort of a "contrived" attraction, a narrow, winding country road choked with autos, trucks, and farm equipment. It's not that interesting. The most interesting thing is the cities on the Road, and unless you take days (I spent 5 days on the road in 2007), you won't have time to see them. The two most interesting stops on the RR are Füssen and Rothenburg. You can get between them in a little over 5 hours by train. You can do the entire trip by train, Füssen to Rothenburg, with a Bayern-Ticket for €28 for up to five people.

The RR bus stops only briefly so you spend most of your time on the bus. Not a good way to go.

The RR actually bypasses many of the more interesting towns and cities in Bavaria, like Bamberg, Nuremberg, Weissenburg, Regensburg, Bad Windsheim, and Eichstaett.