OK....sorry if this is a dumb question but what is the advantage in having carbon cranks. Weight? Stiffness? Is a carbon crank lighter and stiffer then a Dura Ace crank? I just purchased the new 5.5 Madone with full Dura Ace except for the compact carbon crank. I want to switch to standard. Not sure if I should go with carbon or the Dura Ace crank...