Weight is weight. The difference is going to be stiffness of the frame. If both are stiff, then it's not going to make a bit of difference what the frame is made out of. I have both a steel (Bianchi EV Boron) and a carbon (Masi 3VC) frame bikes and don't notice a bit of difference in either. Both are quite stiff and light. Usually the price of carbon is better than a comparable weight steel frame. Light weight steel is expensive. Carbon doesn't have to be.