In addition:

- no mic input or vocal harmonizer
- no aftertouch
- non colored screen
- less wattage speaker output (I think)

But the 500 (to me) sounds extremely good too.

zuki
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Live: Korg PA4X/Zed 6FX/EV Everse 8s/Senn 935/K&M stand

Studio: Korg PA4X/Yamaha DGX670/Yamaha PSR SX900/Boss BR900CD/Tascam DP24SD/MTM Iloud/Senn 935/K&M stand/Shure SM57/Sony C80 (2)/Blue Encore 300