I'd buy the M10 or R-05, whichever is cheaper. I own the M10 but, if it had existed when I bought it, I'd probably get the R-05 instead. I prefer Roland's button setup, don't like the M10's non-lockable wheel, and don't believe that it has "incredible preamps and A/D" as is the "conventional wisdom" here (which has never been actually tested in a comp, AFAIK).
The only other consideration would be battery life. My M10 has been on the same set of Energizer Lithiums for something like 50 hours now. I don't know if the R-05 is that good, but that's also a consideration.