Hi! I asked WD about the differences of the two versions and i'm not sure what it means that they said to me. Maybe there really is some difference, or they are not saying the truth.
Q: "I'm interested in the new Raptor drives, and would like to know if there is any difference between the two models (except for the look). I mean is the Raptor X better optimised for deskop computers or is there no difference in the firmware?"
A: "Both the new 150 gig raptors have 16 MB of cache, NCQ, 1.5 Gigabits/ Second transfer rate, and a 4.6 ms seek time, and the same firmware. But the WD1500ADFD is the Enterprise version of the new Raptor, for use in RAID, servers, workstations and enterprise storage. It is optimized for use 24/7 and includes the RAFF technology. The Raptor X, clear cover, Gamer version is the other one. It does not have RAFF and is for use in desktops for fast performance. It is the WD1500AHFD."