Yeah...I used to own an M50 & it is indeed,a fantastic workstation for just over a grand,but the key action is not all that great,the pianos suck & the sound creation is limited.
TheK2600 has 76 semi-weighted,full size keys and with it's V.A.S.T. sound engine,you can build sounds from the ground up(whereas the M50 is a dead end,sound-wise).
Besides which,I don't really place any stock on statistics....so I wouldn't concern myself with what the general populace deems as being popular or "trendy".
-Elwood