My coworkers Core i7 960 puts my Dell Prec T5500 to shame

What took my computer over 20 minutes to render (and it wasnt even finished when I aborted) took his computer 1 minute!  What the heck is going on?  His computer shoes 8 threads to my 4.  Is this a difference between the XEON and the Core i7?  I feel jipped.  It seems that it would have been better to save a bunch of money and get a core i7 over the XEON.

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