Hi James here. The M1R is the better one. All Korg's numbers are backwards. EG...THe T1 is Bigger and better than the T3.
On the M3R you cant program in Effects to any sounds. You can only to that in COMBI mode. On the M1R you can do Both.
The M3R does not have a Sequencer the M1R has. There are lost more things the M1R does over the M3R.
So I would say..buy the M1R. But the M3R has slightly a better selection of sounds. Like the one called Sparkles. It's nice for Christmas Songs. One more thing..The M3R will only read the PCM DATA CARDS from the M1 and M3R. It will not read the M1R prog data cards.