A comparison of SCSI and ATA concludes that the difference lies in:
1. Connectivity – ATA supports internal storage while SCSI supports both internal and external storage
2. Speed – ATA speed ranges from 100/133/150 MB/sec while SCSI speeds up to 320MB/sec
3. Hot Pluggable – ATA does not support hot pluggable while SCSI does.
4. Expandability -ATA is easier to set up. SCSI has great expandability but its very expensive.
5. Cost – SCSI is high cost and better performance than ATA
The difference is the interface :-