My two cents:
The X1 still has the best direct song play and chain play. Yamaha can play songs from the hard drive, but you can only search for the next one while one is playing, you can't play a chain of songs (but the next operating system might change this!). The X1 has the weakest grand piano compared to both the Yamaha and the Korg PA80 (to my ears and most of my customers). The Korg can search and load a second song while the first is playing, but it's search system is not as quick as the X1. Korg PA80 has the most big band, Fox Trot and Swing songs of the bunch.
These are just a few thoughts on the subject. I could go on for hours, but in reading these few posts I just thought i'd put a couple of thoughts down.
George Kaye
Kaye's Music Scene