I have my Velociraptor in a SilentDrive and am very pleased with how inaudable it is. Granted that without the SilentDrive the noise is about the same as a modern hard drive. Until something significantly faster and better comes along it will be on my shopping list but I don't think SSDs are good enough yet.
Back on topic, I'm interested in a 1Tb drive for backup and can't decide between the two. I read the Tom's Hardware review (that was linked earlier) with interest. Both Samsung and WD seem good choices and there is no clear winner. I think I'll go with WD because I have more faith in their reliability but would be interested to hear other readers' comments.