Things that made me choose SD1:
very realistic styles and sounds
HD storage and quick access for practically unlimited number of personal settings, new styles etc…
stack of four independent sounds for right hand
footswitches for various functions
onboard vocoder
support for midi accordion
76 keys
I would by another Ketron:
because of the above reasons
stable hardware
very good support and ability to repair, change and add SW functions
What I would like to suggest for future implementations and models is a mode (controlled by a footswitch) in which keyboard would be able to follow the tempo played by musician (to make accelerandos and ritterdandos).
Luka