While hard drives sport a mass of technical specifications that fascinate PC enthusiasts and PC magazines that feature them, most aren't worth your or any business owner's time.
Longtime brand-name manufacturers like Quantum, Seagate, IBM and Maxtor offer nothing but fast IDE drives. Minor differences in speed are classified primarily by the revolutions per minute (RPM) that the drives' platters spin. Most 10,000 RPM drives are faster than 7,200 RPM drives, which, in turn, are faster than most 5,400 RPM drives. Also, larger-capacity drives are usually faster than their smaller cousins, so you can shorten your evaluation process by buying a larger drive with higher RPMs.
Within those classes, evaluating the small differences in drive speed only becomes worth your time if you have a special purpose in mind--a graphics workstation or LAN server, for example. The choice for the past couple years has been Seagate's 10,000 RPM SCSI Cheetah, with its large cache and use of the familiar SCSI bus. IDE drives like those listed in the accompanying table are easily installed in desktops, but the Ultra ATA/66 bus they use to communicate with the computer is much slower and less robust than the Ultra2 SCSI or Ultra160 SCSI buses that Cheetah uses.