Even among carbon bikes, ride quality can vary wildly. There are carbon bikes that ride smooth as glass and carbon bikes that will rattle your teeth out. I have a Calfee carbon bike that is as smooth as anything I have ridden. I also have a Panasonic steel bike I bought in the 70s that was so harsh I gave up on riding it. I also had a steel Raleigh that was my favorite bike of all times. If I could find another bike like that Raleigh, I would buy it immediately.

I think design and geometry have more to do with the ride than the material that the bike is made from.