At the present moment the Core 2 Duo is the best for performance, but I don’t see it staying that way for long as AMD/ATi start bringing out their new stuff in the next few months. i have always prefered AMD chips simply because i have had fewer stablity problems with them, also even though some people like to dis the semprons, don’t they OC like crazy mine is w/ mostly stock cooling and will out perform alot of newer socketed Athlons(equal to about an Athlon 3700+ on s939).
For real world performance on my computer, I can run 3ds rendering hair and fur designs, have phootoshop open int he background with just stuff there, DivX playing movies, and Firefox with about a billion (approx. 10)Tabs open and still be able to work(granted rendering is slower)
btw the stock speed for my CPU is 1.8GHz