One thing to keep in mind is that most people seem to go for less aero positioning on a CX bike...perhaps thinking in terms of something midway between a road bike and a mtn. bike. I would personally not want to be as aggressively positioned on a CX bike, since you're going to want some degree of "body english" ability. And a bigger bike will weigh more, which you'll feel every time you have to cart that baby over a barrier or up a hill.