ok I'm thinking of getting a MD....how does the noise of the inputs compare to an M-1?
Since I use the M1, HiMD, and MT for recording ambient and quiet sources almost every day, here's my personal analog combined noise and sound quality comparison:
M1 > HiMD > MT
If it's just the noise performance you're interested in, ignoring any source/mic noise, my M1 has around 90dB S/N line-in, while HiMD is closer to 98dB S/N (nature recordists group have one measurement closer to 100dB), so
HiMD > M1 > MT
If it's just MD you're interested in, based on my experience with the MZ-R50, a great little deck for its time:
M1> MT >> MD
I found the ATRAC v4 compression on the R50 to be audible and the input circuits relatively noisy, so I can't recommend MD for modern applications. No digital uploads are available either. Happily, Sony apparently chose to use the same or similar analog input circuits in the SBM1, M1, and HiMD. Sure we're not talking about a 722 here
but for around $200 HiMD has no competition.
Sorry to use a cliche, but: It all depends on your application, so let your own ears be the judge! I spent a little extra money and bought my HiMD gear from Fry's Electronics brick'n mortar just to try out and return if the decks didn't perform. I had one bad RH10 and one bad MT that I had to exchange. You usually can tell in the first 24hrs...