I would imagine the MM6 is better than the PSR 550 - I have the PSR 420 - which is basically a general midi instrument - good drums - and replaceable ROM.
The MM6 is based on the MOTIF series you can check out the models and compare them on Youtube before buying - the MOTIF is an awesome instrument.
The PSR series is considered dated however the Youtube link below sounds fairly good.
The PSR will like as not be much cheaper than the MM6 - I think you ought also to check out the DJX machines - they're old - but quite amazing.
I'd definitely choose the MM6 if I had the cash!
The MM6 is based on the MOTIF series you can check out the models and compare them on Youtube before buying - the MOTIF is an awesome instrument.
The PSR series is considered dated however the Youtube link below sounds fairly good.
The PSR will like as not be much cheaper than the MM6 - I think you ought also to check out the DJX machines - they're old - but quite amazing.
I'd definitely choose the MM6 if I had the cash!