sb-r200 vs sb600

i am looking at getting two slave flashes to go with my sb800. is the only advantage of the sb-r200 its ability to be mounted to a macro lens ring? how do these flashes campare in power output?
EDIT: BTW feel free to move this to "Absolute Beginners Questions" if thats where it belongs.
EDIT: BTW feel free to move this to "Absolute Beginners Questions" if thats where it belongs.