If you use the sampling feature for loading samples larger than 32mb then the pa800 has an obvious advantage although the sampler is exactly the same in terms of its functionality, also the polyphony is larger (128 notes compared to 62 on the PA1X). However for live use the sliders on the PA1X come in so much more handy for controlling volumes, and organ bars in real time. The PA800 does not have these manual sliders and to my mind that was a silly ommission by korg.

Lastly the PA1X has a better speaker system in terms of the inbuilt speakers when compared to the PA800 and also a better vocal harmoniser.

Now that the version 3 has come out on he PA1x it is even harder to choose between them but i am convinced you wil have a blast no matter which one you keep