Netapp makes good points in their response to the paper on average failure rates. Ignoring the intrinsic marketing in their document, the information in there is invaluable.
As indicated before, PT Barnum would be pleased with the vendors of the higher priced product promising, but not delivering, higher reliability.
We had noticed this for a while: failure rates are about the same. And in this case, why would you use the more expensive product which promises lower failure rates?
One reason, and unrelated to failure rates. Seek speed. Current SATA is 7200 RPM. 15k RPM FC/SCSI can still out-seek SATA. Until SATA get 15k RPM speeds, and I don’t think there is much pull in this direction, the SCSI/FC crowd will have a market. A small one, but a market none-the-less. A market having nothing whatsoever to do with reliability. Only seek performance.