Thanx in advance

Features are around 75% the same, user interface is easier in the SD1s, you do not have to remember banks or sound/style numbers, and, most important if you play styles real time is that you do not need the memory expantion (in the X1 is a must), the SD1 reads the patterns direct from the HD....newer features and this is comparing teh X1 with the original SD1 OS, now, the SD1's 4.0 OS.....with the "cleaner sounds" is a lot more......hmmm.......Better!!!

Fill-in, variation, ending, intro buttons on the "wrong" side of the X1. You can't easily reach them with your left hand.
DonM

Ditto!!! Ditto!!! and a big, big difference in the piano sound.

Armando

So the Sd-1 is better in so many ways for the live player......