The only advantage that SK880 keyboard has over Genesys is the 88 keys IF you are looking for 88 keys. In my humble opinion, if you are looking for a workstation that does it all, there is no escape from either Genesys series or SK series.
SK880 is the best possible workstation in its operating system, logical organization, and powerful integrated sequencer. Genesys just got even better. In performance, after you learn the both keyboards, you cannot beat the instant and easy control of your live performance.
If a powerful integrated workstation that offers styles and style-integrated sequencer is what you need, Look no Further. If you need 88 keys now and you have money, I would get Genesys and 88 controller. If not, then consider sk880 after you look hard at the sound and style quality of it:
Not that Sk880 is bad, but all the new keyboard have gotten better technology and far better sounds. How much better? Enough to make me want to shop for a new keyboard. But let us say, you already have a good keyboard with excellent sounds such as Tyros, SK880 will be excellent complement.
What about the sound quality of Genesys compared to other keyboards? I do not know.
What if you really want SK880? I recommend the following must:
1) Listen to SK880 for long time before committing. Make sure you listen to other new keyboards so you will know what you are missing. But if it could work for you, hey, excellent.
2) Make sure you buy the following options: Harddrive + 8MEG of Battery-backed DRAM.
In conclusion, I love my SK880 and I still use it to produce professional results. The sounds sound very good. Yes, I am looking for a new keyboard to buy that is lightweight, 61 keys or so with the best sounds and styles; but not to replace SK880 because it cannot. The only keyboard that can replace SK880 is Genesys88 when it comes. Let them take their time and enhance it completely with even better sounds and styles and more features.