I have a TCD-D10 Pro. At something like $2750 it was a very poor investment; I used it only a dozen times or so. Despite having "professional" specifications, its microphone inputs (which didn't offer phantom powering!) were easily overloaded by signals from professional condenser microphones. Its line inputs were noisy and insensitive, and its meters were inaccurate. To use its digital input, you have to buy a proprietary input cable that used to cost ca. $125, but which became unavailable during the lifetime of the product.
The "II" version adds a very poorly-implemented DC offset filter at the output. There was one other difference which I no longer recall specifically, except that it was somewhat advantageous.
On the positive side, the unit used a full-size head drum which makes the unit less susceptible to dropouts in playback than the half-size drums used in the miniature decks.
I've never used a PCM-M1, so can't comment there. Supposed to be an OK little deck, but it's just their consumer unit with a different SCMS arrangement (adding the ability to record through its digital input at 44.1 kHz), no? That's useful, but doesn't make the deck professional.
--best regards