Based on what you've posted, I prefer a closed arranger keyboard, but I would like to add this...
My mid-range Yamaha PSR-S910 allows me to edit sounds, styles, effects, registrations...I can import new styles, and sounds (edited on-board voices) and customize the instrument to my needs and style of playing.
If one is prepared to put in the work, a "closed" keyboard can be very adaptable to a player's expressive style and needs.
Maybe not to the degree an open system can provide, but, still pretty flexible and personalizable nonetheless.
Ian
[This message has been edited by ianmcnll (edited 04-22-2010).]
_________________________
Yamaha Tyros4, Yamaha MS-60S Powered Monitors(2), Yamaha CS-01, Yamaha TQ-5, Yamaha PSR-S775.