I'm a 2000 owner and I've never played an 8000 but I went throught this debate myself. You can download the manuals for both keyboards from Yamaha, which might help.

My conclusion was that the "extras" on the 8000 (aftertouch, extra lead voice, hard disc, sampling) were outweighed by the 2000 being newer, having more variations, and being more portable. As I didn't see myself using sampling (and I dont use vocal harmony yet) then the hard-disc unavailablity on the 2000 was my biggest debating point but the floppy-swap operation on the 2000 is pretty quick and I have no regrets in choosing the 2000.

No-ones mentioned the sampling capability on the 8000 so far - does that mean no-ones uses it?