In addition to what Miguel says here I would like to say this:
In as far as I have any experience with Yamaha, you know I have
loads with Korg, one of the most outstanding features of the Korgs
from the outset ( i3, etc.) was the fact that their styles run over at least 2 but often three to 6 bars, whereas Yamaha has often stuck to 1 or 2 at the most, hence sounding much more repetitive. Over the last three months I have owned the PSR3000 next to the PA800 and this has only confirmed my views. However I cannot speak for the Tyros 4, I am sure Ian or others will fill up this void.

regards,
John Smies