When you say a SCSI drive what do you actually mean. SCSI is most commonly used for hard disks and tape drives, but it can connect a wide range of other devices, including scanners, and optical drives (CD, DVD, etc.).
> what factors would you consider when selecting a SCSI drive?
If you live in the northern hemisphere, you need to get one which spins clockwise, whereas if you live in the southern hemisphere, you need one which spins anticlockwise ;)