I'd say it depends mostly on what you want it to do.
Western Digitial (WD) and Hitachi (IBM) are built for business applications, like servers or client terminals. Machines that have very high useage. Basically built to last, but you won't see them winning any performance reviews as due to this reliability and stability they sacrifice performance.
Seagate (especially thier new line) is build for home and mobile users. This is because they're designed for fairly heavy useage, but with features to cut-down on the drive spin times, and the new series has a cache that dumps immediate operations to it allowing for much faster hibernation and wake-up times.
Maxtor and Fujitsu are cheap, and good for light users. No real performance, no real reliability.