My own personal experience - Less broken bones when I've crashed (better protection!. & more user friendly.!..
It's handy not having gears when you've got a dodgy water-swollen ankle and also handy not having a chain to oil/tighten/replace too. And having under seat storage for two full-face lids is a godsend. Wouldn't say no to a yam R1 for the weekends though. Now if only I could persuade her indoors to have both...
I looked at an R1 motor for my atv... But I couldn't be bothered with rebuilding the motor and modifying the frame