I have 2 WD 120 gig HD's. One is 5400 the other 7200 rpm. Both are UDMA 100. They bench within a few points of each other. Seek time is marginally faster on the 7200. The 7200 is one of the quitest drives I've ever had. Quiter than any of my system fans. The 5400 is completly quiet. Runs cooler and uses less power. I wish the 7200 was a 5400