I sell both of these products at my store in Los Angeles. Right now, the WK3000 offers much more in features and in sound quality. The difference is that Yamaha is a better company to deal with if you need help but the sound quality of the Casio for Piano and Organs beat the Yamaha. Guitar wise, they are both good. Brass is better in the Casio. The Rhythms are pretty equal but the Casio is still better in my opinion. Also, the Casio has a smart media card option for saving and playing and the Yamaha has none. Also, the Casio has programable synth possibilities and you can choose any sound you wish to split where the Yamaha doesn't allow so many sounds to be used in split mode. I also can tell you that the effects processer in the Casio is totally programable and the Yamaha is not. I guess you can see which one I like better!
George Kaye
kaye's Music Scene
Reseda, California