I have both keyboards. The Casio is great as a piano. I love the feel and the polyphony is great. I do not use the other functions of the Casio. The Yamaha MOXF 8 is considerably more costly. It has a great piano sound and all of those arpeggios. Almost 7,000. You can create many performances. I would take the MOXF over the Casio PX5S only because of the ease in which you can create performances. I think some of the sounds might have come from the Tyros line. IE: Guitars. I had a Tyros 3 and I thought I heard some of the sounds in the MOXF. I may be wrong, but the sound are quite good, in my opinion. If the choice were piano only, then I would not rate one above the other. I could be very happy using the PX5S for piano sounds only. To me the Privia is greatly underrated by people. I play classical music and the PX5S can take anything you throw at it. I hope this helps you in some way. It is pretty hard to put the PX5S up against the MOXF. Yamaha has been making this line for some time now. They have it down real well. The MOXF was a keyboard best buy. You certainly do get the bang for the buck. If you can get the MOXF, do so. You will not regret it, as you did not regret getting the PX5S.