Running the same tires... same rims. Of course it is a complicated system, so you can never compare it 1:1. Fact is that carbon bikes tend to ride more comfort

Running the same tires... same rims. Of course it is a complicated system, so you can never compare it 1:1. Fact is that carbon bikes tend to ride more comfortable, if they are designed for it. Also the frame can be shaped and put together to flex in the right directions, which is harder with aluminium. Then again, there are also endurance bikes (many 1000s of km's a week) made from titanium (J. Guillem) which are comfortable and also have much simpler shapes than carbon frames.