The X-box will be easier to develop for, but it's based on a relatively ancient architecture. And don't let the MHz fool you, the PS2 is still faster.
Microsoft has to overcome both it's image as an evil empire, and the sheer momentum of Sony; PS2s got a head start and have a proven record in the console market.
To the next person that quotes specs, remember that most Americans don't understand them and as a result, they fall back on big number good when shopping. Why do you think that VW sells so many VR6s when the 1.8T has better performance, HP, economy, and price? Bigger number of cylinders and bigger number of cc's/cubic inches.