I've riden my '04 Roubaix Comp. for several years and several thousand miles. This summer I was fortunate enough to build up a 2010 Roubaix Pro frame/fork ,etc. While components on both bikes are not the same, they are certainly close to equal with no weak links. The one glaring difference might be that the Pro has a compact crank. The Pro is a bit lighter, but not by much. Now for the issue that puzzles me. Why would the Pro leave me feeling drained after a 30-40 ride compared to the old Comp that leaves me a whole lot fresher? Maybe it's just a matter of getting use to the new frame ( only 400 miles so far), but I would have thought the opposite. They're both very smooth so it's not like I'm getting beat up on the Pro.....just that as silly as it sounds, the Pro seems to take a bit more of a push to get it going. Am I missing something about modern frame dynamics here? Thanks for your thoughts and I hope everyone has a great Labor Day.