I believe I've discovered an advantage of the M10 over the R-09HR that I haven't seen mentioned before. When I change the recording level on my HR during a performance it leaves tiny gaps in the wave file that make the unedited file sound awful, although often you can edit out the gaps and can't hear the difference. This does not happen with the M10 and (surprisingly), the old R-09.
I know we don't want to change levels during a performance, but occasionally it may be necessary.