Until Yamaha add in the capability to drop into a loop on anything OTHER than the 'one', rather than cuing them up a bar in advance, there's a DRASTIC difference between the Motif's and the arrangers.
On an arranger, you hit the fill button, it IMMEDIATELY drops into the fill, still in time with itself. Unless I have heard wrong, there's nothing that can do this on a Motif.
AFAIK, you also can't change inversions on bass and keyboard parts. Root only (unless the arp is written as an inversion), I believe.
Want to remind yourself how arrangers used to be, right when they first came out? Get the latest WS's...
