I certainly do not agree that the Roland was the best in fact I thought it performed the least out of the three. But it is a bit unfair. The RD700 while sporting some decent pianos may not have the best of their synth sounds in there. And their pianos were still not in the league of the Kurz anyway. I would like to hear the Roland Jupiter 80 up against the Kurzweil, that would be a much fairer test.
 
The Kurz Artis while primarily a piano instrument as well does have some of the PC3 sounds in there and they do sound as good as the synth but it still only represnts a fraction of what is in fact in the synth.
 
Nords I have found are good for organs and electric pianos, they are strong on those but not much good for anything else. I have recorded all their models at one time or another here in my studio and I still have that view. It is not money well spent. The Kurz can do the organs easily and the electric pianos too but a whole raft of other stuff too making them far more versatile.
 
I agree with backwoods in that you just have to really figure out what you want from the instrument and try them out. For example it is studio performance I am after and the Kurz is one of the best in that situation. For live playing you may need a different approach. Although I have never heard a Kurzweil sound bad live either.
 
Some more comparisons. These are quite fun to watch. This one is quite cool. I must admit I like the sound of the Nord in this too. Update: I was at a party last night and chatting to a guy who owns the Nord Stage or the one that is supposed to be able to do the synth sounds and he backed up my original thought in that he said it is way inferior in the synth department compared to others that are very strong in that area.
 
http://www.youtube.com/watch?v=uX0aEnasa6Q
 
And another one:
 
http://www.youtube.com/watch?v=krluY7teTfI