the Opteron 850 has quad processing ability, it does what HT on a P4 does, but emulates 4 processors. when you have a dual Opteron 850, buth with quad processin turned on, you have 2 physical, but 8 virtual processors
I'm not sure exactly which one I would choose from. I only say that because I haven't tried out AMD's latest line of processors compared to Intel's. Of course, by the time I get another computer with an AMD processor, this post will be long gone!!!