I own both...
I'd say they are both very comfortable. (almost equally comfortable....slight advantage to RR, and that is only because it takes a lot less time to find a sweet spot)
if you sleep with your knees tucked up, go with the BB
with my BB, I can only sleep on my left side(facing zipper/entry).... sleeping on right doesn't work for me-probably due to shape/cut of hammock--RR you can sleep facing left or right. (Some may feel comfortable laying on right side in BB, it may only be an "issue" with me)
It probably would be best to get both and give them each a try.
If you are backpacking, the BB would be the lighter choice of course.