Generally Intel's chips are better for multimedia because applications like games and movies because they are very predictable, so the inefficiencies of the P4s 20 segment pipeline are less magnified. AMD's are better for less predictable software like CAD and other business type apps. This is because they only have a 7 segment pipeline which means when the processor incorrectly predicts the next action, it only has to flush 4 or 5 segments, instead of 15 or 16.
Like Rbstr said though. Right now AMD's Athlon64 is the best overall for the simple fact that it's got a butt load of cache.
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