Bought an SMH10 yesterday. Did not buy the newer R type, even though it was close to same price.
Guy at the parts counter, whom I've known for years and has never steered me wrong, said people who have used both find it easier to dial the knob than press buttons. Regardless, battery on the old unit lasts longer, can be recharged while riding (not sure how difficult this is on R), and old unit has a socket where I can plug in my non-Bluetooth MP3 player. Yes I know there is a $12 adaptor to resolve that. Considering it all, thought it was better to go with the older style. Fits my age group.