Originally Posted by
carleton
So, I would choose a frame based on it's reputation (via reviews or whatnot) more so than just it's material. There are plenty of flexy steel/aluminum/carbon frames just as there are very stiff steel/aluminum/carbon frames. It's up to the design.
That's a very important thing to note-- it's the design of the bike, not the material that makes a bike stiff or flexy. I've ridden steel bikes that were really flexy, and others that were really stiff. Carbon can also be as flexy as you want it to be, and in whatever directions you want, depending on how you build it up. A lot of CF road bikes are pretty soft, but something like the Look 496 or 596 is stiff as a brick.