My old bike was aluminum with a carbon fork, and I was generally okay with it while I had it. But on my first ride on a carbon bike, I noticed a difference in comfort due to less road vibration. And it wasn't on chipseal roads, just ordinary old asphalt with some areas of filled-in potholes.

So I would say that if you can afford a Madone, get it instead of the Lexa.

I think the lower-end Madones have the option of triple chain ring vs. compact double, if you want a triple. The more expensive models (with more expensive components) are compact double (or regular double?) only.

Also I would not go lower than 105 in terms of components. My old bike had a few Tiagra components, including the front derailleur, and I had lots of problems with it. It finally broke due to being adjusted too many times and was replaced with an Ultegra, which solved all the problems.