The T-series is a signficantly better instrument than the M1. The T series has more samples in ROM and higher quality samples and effects than the M1. It also has a better LCD display. Many of the sounds in Korg's current gear is still from the the T-series ROM.

Of course depending on the price of this used equipment you may want to check into a Kurzweil K2000.

Mike Martin
Kurzweil Music Systems