Very good discussion thus far. I'll throw another question out there just for grins - if the compact frame is so much better for the stiffness required of a racing bike and given that frames resembling the compact design have existed since the late 19th century, why did the horizontal top tube design become the standard for the first 1 1/4 century of the modern bicycle? Especially since there were no oversized carbon tubes and oversized bottom brackets with outboard bearings and all that...given the limitation of their materials you'd think they would have wanted the stiffest frame design they could get.