Anyway this is what Ive found.

The Su resamples only in mono.
The XL has no realtime controls and less filters.
The Su has more std memory.
The XL has more audio outs std and optional.
The XL has SCSI standard.

The Su is less expensive. (w/ expansion board and optional SCSI interface its same price as std MPCXL.)

SU = $1000 scsi=$150 exp board=$150
XL = $1200 efx=$300 exp board=$250


Anyone else?