Common sense gets more power!!!!
Dells prices can be a bit mad. Infact i bought a duel quad core 2.33 na Dell Precision 7500 for about £1000 less than a mac pro. Why? because i get a choice about what goes in it. It was also a feck lot faster than the spec given in this comparison, despite lower spec cores i had twice as many, more memory, 10k rpm hdds. Buy with common sense then you get a good price. You also need to add promotions and deals which dell have on 24/7.
Also that Mac needs a warrenty pack £250 Office £200 more than than the PC cuz u cant get OEM. Adds up really fast on the Mac.