Only SCSI-2 UW specification had a limitation of 1.5m (~4.5 feet)and that is with the old-school 50pin cable. Any modern SCSI-3 LVD HDD has a limitation of "only" 12m (meters) and the HVD has a maximum length of 25m.
How can that compair with IDE limitation of 18inches (~1.5 feet)???
BTW multiple drives chained on a single channel is NOT the only advantage to SCSI........ that is just one of the "perks"