The Desmo has to be the most uncomfortable bike for the streets I've ever ridden...very aggressive seating, hard seat and suspension, poor handling at street speeds, too much heat from motor/exhaust, and just forget about it if you're stuck in traffic. But on the track, completely opposite. Fast as hell, nimble, turns in fast, loves to spin up the rear tire, just fun fun fun!!! This bike is a pure race bike that can be ridden on the streets.
The R is more user friendly for everyday street use, as well as a track weapon. Seating/ergonomics still aggressive, but not as extreme as the Desmo. The twin motor configuration is better adapted for the streets...torque wise. Handles great both on the street and track. Just a great all around bike. The R is a street bike built to go racing.
Just my .02