I would go with the Roubaix. I have a CAAD9 R6 and I got a great deal on it...but....I should have gotten the Roubaix. I don't see a lot of geometry differences between the two bikes looking at the measurements but I feel it (picking up my Roubaix soon). No matter what we've done with the CAAD, I'm sore after an hour and a half, and my teeth are falling out from the stiff ride. We've shortened the stem and raised it up, and now it's REAAAAL twitchy and just not a pleasure for me. Anyone want to buy a CAAD in GREAT shape with Tiagra components, 54cm???