Today SCSI technology is widely used for servers due to their hish performance efficiency over SATA. For detailed comparaision please go through the link below: http://en.wikipedia.org/wiki/Serial_ATA#SATA_vs_SCSI
Most of the servers we use have SCSI drives we do have a few SATA machines and the SCSI do perform much better, they do cost a bit more than SATA but worth it in the long run as they are much faster and live longer.
SCSI are faster and long lasting
but they tend to lighten your pockets at the same time!
I would suggest SCSI if you have the $$$ for it,,,...
else a SATA would work just fine!
I think most people have said it, but just to add my vote. If you have the cash SCSI is the best. But if you are working on a budget, the SATAs will work its just not going to give you the fast RPM speeds of the SCSI drives.
A good SATA Drives would be fine for average or advance usage. However if its for a monster servers such as larger scale VPS node etc then SCSI would be a must or you will end up having Disk IO related performance issues ones the drives get filled in.
I would prefer SCSI drives for VPS nodes or DB machines, but otherwise for hosting in general, SATA will be more than enough to get the job done, and it's cheap.
SCSI gives a good RPM around 15-20000 thousand comparing with 8000 of SATA . The speed and reliability of SCSI is more then SATA although the price is a down side when comparing the two . I would go for SCSI if have that much money for performance .