I used both keyboards last night. The difference in sound was very striking. The Kronos is like a super fidelity keyboard. There's more punch, highs, lows and overall just more sonically than any of my other keyboards. The Kurzweil programs sounded much more defined in terms of sonic bandwidth.
What I love about the Kurzweil is that those programs just nail a vibe. The programs are so well done that if I want to dial up a mood or evoke some kind of memory, the sounds are there. VERY NICE! I am also used to the programs after using it for so many gigs that it was a familiar and friendly sound.
I found myself using the PC3 for sounds that evoke a cool vibe and used the Kronos for more broad generic sounds.
For me, the PC3 stands on its own in a different sonic space than my other keyboards. Although the PC3 seems like it may compare with the Kronos in capability, the reality is that they are very different for live use. The PC3 is a keyboard where most of the programs were based on recordings and some do really nail the vibe.
The Kronos is more like my S90ES and I will need to compare those two. When I play the Kronos I think... this is the best sounding keyboard I have heard. Very similar to the feeling I got when I used my S90ES for the first time.

