I've got two Maxtors and they have been dependable drives with great warranties. Better than some of the Western Digitals I've had in the past. Right now, the IBM 60GXP drives are about the best (I have two fairly new 40 gig drives of this model). As far as which one to use of the two drives you listed, good question. It's about a toss up as far as speed goes. Maybe run each one and benchmark them using Sandra. I might lean towards the Maxtor, the slower RPM will be quieter, cooler, and more dependable than the WD 7,200 drive. Are you sure the WD is only Ultra 66, I thought most of the 7,200 RPM drives were Ultra 100?