Numerous comparisons have shown that AMD Opterons are way faster than Intel Xeons for anything related to video (Lucasfilm bought 1,000 Opteron workstations as soon as they got wind of them, I imagine their existing Intel boxes were discreetly dropped off at the loading dock for pickup).
AMD X2 dual core processors are also much faster compared to Intel D dual core processors. Note that AMD CPUs may even be more expensive than “corresponding” Intel CPUs, AMD has seen their performance premium as real value.
AMD has a much more advanced CPU architecture, and a much faster internal bus that doesn’t keep the CPUs waiting.
Intel has fired a whole bunch of executives because of this lost battle, but they are not expected to catch up until 2008-2009.
Whole brand name (Gateway, HP) PCs with AMD X2 4400+ for example are now available for about $1,000-$1,100. The only thing holding AMD back for the moment is manufacturing capacity, where Intel of course has a lead.
There are also truly great motherboards from Asus and some others if you want to build your own machine for less.
The only thing to watch out for it to get a motherboard with nVidia peripheral chips, rather than with the VIA chips that have given AMD an undeservedly bad name in the past.
The vast majority of Hollywood companies are buying AMD-based workstations now, they can’t waste time waiting for slower technology to do effects rendering.