As stated the 9000 pro is built better.... It's sort of built on the base of Yammies old EX-5. The 9000 Pro does have the keybed of the Yamaha EX-5 though.., which is a very nice feeling keybed. Sounds and styles aren't bad (a bit dated by what's out there today), but the PSR-9000 and Pro version wouldn't have any problems putting out a nice sounding mix.
There are CPU issues as Ensnareyou pointed out. If you do some heavy sequencing.., or get a lot of things going at once (heavy style work with a fast tempo ect.) the board can lag at times. (I do remember this same issue regarding an underpowered CPU even coming up with the Yamaha PSR-740.., that was also still being used by members here around the time of the PSR-9000 and 9000 Pro).
**on a side note..., when home in Erie PA a few years ago I was at a local music store that had a used 9000 Pro on the floor. I ended up demoing the thing for a few people
I do remember hitting the CPU problem with one of the fast bigband styles (can't remember which one).., but using that style..., dual voicing.., using the sustain pedel ect.., did bog down the CPU. (More than it should have too).
[This message has been edited by squeak_D (edited 11-24-2008).]