I have two bikes- a steel one with carbon forks and an all carbon one.

Yes, the steel bike is 5lbs heavier than my carbon one, and it has a different gearing on it. If I am going to do steep steep hills, I'd probably use the steel bike mostly because of the gearing as I have mountain bike gearing in the rear.

However, I find that I prefer my carbon bike for most of my rides. It's very comfortable and very fast if I want to zip down the hills. I also have found that I recover more quickly after going up hills.

IF you really want to get the full scoop, I Googled this subject and found an interesting article that explains every bike part and what it does. It also describes the different types of frames and how they are made. Excellent for learning terminology and understanding bike design!

Google: Advantage of carbon fiber road bikes.
Article I found: Racing bicycles-Wikipedia, the free encyclopedia.