nambit is right about the mhz myth, i don't have the link anymore (/me bashes head on table) but like any number associated with a product, 83.56% of it was invented/misconstrued by the marketing peeps.
i own a ps2 and love it, the fact that sony didn't change the controllers from ps1 is what really sold me over the xbox, despite the happy thought of screwing billy out of a linux box.
game availability is another sticking point (read: pain in the ass), like renegade mentioned, ps2 has GTA, xbox has splinter cell which is an incredible game, and gc has pokeyman, if thats your bag.