Oh yeah, you asked the right question if want a lot of different opinions. I agree with Uncle Dave and Bluezplayer. I think the 9000 Pro has the edge in the piano department. Plus as stated by Bluezplayer, the action on the 9000 Pro is great! It's not weighted, but it's got great synth action.. I too used to have the MZ-2000 and I'm with Bluezplayer on that keyboards piano sound. It wasn't the worst, but sure left a lot to be desired. You're going to get a lot of opinions on this subject. The best thing for you to do is go to a local music store and try them out. Everyone's ear for a good piano is different. I just talked to someone the other day who thought the Casio WK-1800 had a better piano sound than the Yamaha PSR-9000 (I of course strongly disagree with this), but it goes to show you you how different we all hear the sound. Try them out for yourself.. We can only suggest what to try, but it all comes down to what your ear likes..

Squeak