Christian,

The Pa2X Pro and Pa800 have exactly the same sound engine. That is why the demos sound identical. Here is what Korg says about the differences between Pa800 and Pa2X Pro:

"If you need a compact and light 61 key version of the Pa2X Pro with built in amplifier and speakers, check out the amazing Pa800. Same incredible sound quality with almost all the most important features as the Pa2X Pro."

Overall the button layout looks very similar both to the Pa1X and the Pa800, but there might be minor differences.

Kind regards,
Tommy