I don't own either, but I definitely like the look and size of teh R9HR
Plus, A LOT of Team Philly and many NBox owners, have switched their big 7xx decks, into a simple and smaller 24-bit ADC/Recorder combo, and is less than a 1/4 of the size of a 7xx
If I had a pair of mics and a preamp, and was sending an ANALOG signal into either of those, I'd also pick the R9HR, but maybe just because Ive heard ALOT more stuff from the R9HR than I have w/ the Sony D50
All of those small, very portable recorders, w/ GREAT ADC's, they've come a long way even since the old Sony D-7's and D-8's. The M1/d100 were a step up, but not by much. Now the R9HR has 24bit capabilities, and has a pretty damn good ADC in it, MUCH BETTER than those older "walkman" style DATS from 10-15 years ago which were even bigger than the R9HR! Like I said, I don't own either of them, but if I was buying one, I'd go the r9HR, maybe just because its already proven reliability in the field as an ADC/24bit Recorder