Had and Alu frame. Jolted my teeth out on washboard roads. Got CF. Much more comfortable. Love it.

My performance increase is more attributed to hard work and development, none the less, I have to believe that weight equal, a CF frame absorbs some of the vertical movement from bumps. Therefore, just as a slightly softer tire is a little faster than a rock hard one, I believe that a CF frame is slightly more efficient, hence faster, than an "identical" alu frame.

The physics is simple. On a smooth track, all the rolling energy is in the forward vector. With a hard tire (or frame) when you hit a bump,some of the forward energy is transfered to vertical movement. With a softer tire or "vertically compliant" frame, a little energy is absorbed by the tire or frame, but most of it remains in the forward vector. At least that's how it was explained to me.

Along the same idea, frame flex, particularly in the BB area, wastes energy. Carbon and Alu tend to me more rigid than steel or TI, hence more of the pedal stroke energy is applied to the crank.

Given these concepts CF delivers on both fronts, hence it has an advantage over the other frame materials. But there is the cost. :^(

Don't know about a CF/Alu hybrid. That may just be the sweet spot for a lot of folks.