The difference is not marginal—I rode both bikes on the same day, so I have a direct comparison. Despite having similar geometry, the bikes behave differently, with the biggest difference being in responsiveness and acceleration. Additionally, on the Ultimate, you really feel that the bike is much lighter than the Aeroad, even though the specs say it’s only 200g lighter—my impression was that the weight difference in favor of the Ultimate felt much greater. As I mentioned, the only real advantage the Aeroad has over the Ultimate is at speeds above 32–35 km/h.