Why?

Pricewise the Yamaha is in the middle of the 2 Casio's. And the only difference between the 560 and the 360 is 20 more rhythms and 20% more sounds?

Soundwise it does not matter to what Casio you compare as they sound identical and definitely require some external amplification or headphones(as does the Yamaha)

feature wise, the only difference is in the polyphony 256 vs 128, but does that really matter to most? i never hear my pa4x that is 128 notes drop any notes, not even when playing piano with a lot of damper.

But seeing the price difference between the 360 and 560 is less then 15% (what you actually pay at Bax-shop or Thomann) there is not much reason to not buy the 560.

To me the best contender in this market is still the Havian. As its the only one that has the same sound and style engine as the higher end products. its a little more expensive, but since prices have dropped, not that much. And there is supposed to be a new Havian 70 on the way, based on the PA 700.