These are the two that I've considered when upgrading to a new arranger, however the new SD5 also has my attention. One thing is simple enough.. if I get the PA1x, the PA80 I have is history. That may or may not be the case if I get the Tyros2, but if it comes down to it and I wanted to unload one of my current boards, I'll likely keep my MZ2000 no matter what happens.

I haven't played either of them, so I can't judge either way. If the past is any indication though, I'd say I'll probably prefer a majority of the Korg styles ( assuming the fills match the variations a little better ).

I'll probably prefer a majority of the Yamaha panel or lead voices, particularly the pianos, e pianos, sax, horns, and guitars, with the notable exceptions being organs and analog emulations, which I'm pretty certain I'll probably like better on the Korg.

The OS will likely be fine on either for me.
The hardest part will likely be finding both of these in the same store to demo, and add the Ketron to that as well.

Good luck with which ever one you decide upon. I'm sure either will be a winner.

AJ