I spend a few hours with both the PX-5s as well as the PX-560

Keyaction is very good for under 1000 keyboards
Piano, synth, E-piano, organ, strings, pads all sound decent to good
Where Casio lacks is the orchestral sounds like brass, woodwinds and such... they are poor quallity

As far as the arranger part goes... just use the Drums and you will be allright, dont expect anything fancy like yamaha or Korg does.
As a stage piano both these instruments fair well, as an arranger the 560 lacks..

The PX5s is quite popular as a stage/midi controller on stage... extremely light and yet a very decent action
Best part, when sweaty fingers, you still have good grip on the surface of the keys..