Biggest thing I've noticed between the M1 and T series is the sequencing memory.

I did a side-by-side comparison of them with an online database I'm creating, and the keyboards are almost identical. What do you expect, the T-series was modelled after the M1 from what I've heard.

Anyhow, the main differences are:

1. the M1 has 100 samples, 100 combinations; the T-series have 200 samples, 100 combinations.

2. the M1 has a 10000-event sequencer; the T-series has a 50000-event sequencer

3. The M1 has a single MIDI Out port; the T-series has four MIDI Out ports (makes it a great controller)

Hope this helps some. I've been using a T2 for about two years, but it's borrowed, so I just (ie: a day ago) bought an M1.