There's a bigger difference between the keyboard Motifs (orig vs ES) than in the racks, but the ES rack has the new arpeggiators and effects, and the extra samples (although the original rack had some of the ES samples already, if I'm not mistaken). It's less of an upgrade from the original rack to the ES than a Motif 6 to a 6ES, but considering how much value the original rack is holding, I'd say spend the little amount extra and get the ES rack. Don't think you'd notice the cash difference!