The better construction is reflected in the probability of unrecoverable errors: <1 in 10^15 for the RE vs <1 in 10^14 for the Black. For large RAID arrays, that is a significant difference in the likelihood of delays from error recovery, failed stripes or lost data.
RAID drives are often packed close together, and the vibration can have a disastrous effect on the speed. The SE's and RE's have extra vibration sensors and the ability to compensate for vibration when positioning the read/write heads.
Another major difference is in the firmware and controller. RAID controllers on a server may be trying to service multiple and completely unrelated read/write operations all over the array, and so the drives have to handle streams of read/write commands that involve operations all over the disk. Enterprise drives are optimized to complete these instructions as efficiently as possible. (In contrast, a single-user desktop drive is more often trying to read or write one sequential file at a time).
Edited by dietrc70, 13 August 2014 - 10:47 AM.