Frank, having no experience with either keyboard, but having experience with a similar arranger from each camp, I would lean (at this time) to the Korg. I say 'at this time' because in recent months I have gone thru a Korg iX300, Yamaha PSR2000 and a Roland G70. I like the Korg styles, the Yamaha OS and the Roland sounds. The Korg styles were definitely more expressive. If you threw a G50 in the mix, I would pick the PA800, S900 and G50 in that order.

BUT, I don't think you can go wrong with either of your choices. Only you can make that final decision. My opinions are based on personal preferences and may or may not be similar to yours. Good luck.