Conrad -- I have not used either the R2 or R3, but the R2 is the one that has 35mm framelines (if you're thinking in terms of a 35/50 kit). Both are M mount (as you probably know), but your Canon 35s will work just fine w/ an adapter. An R2 (or R) and a Canon 35/2.8 would be a terrific combination, IMO: compact, good blend of vintage look (from the lens) and modern metering and vf (from the camera body).