Generally ride comfort is...
Carbon (better than) Steel (better than) Aluminum

Some people have different opinions...but in addition to that different design and manufacturing has made the differences close to impossible to tell just from the material. They even make smooth riding aluminum frames now, to my surprise as I'm rather sensitive to road buzz through the frame. The most comfortable frame I've ridden was definitely full carbon fiber, but I've also ridden other old racey carbon fiber frames that had a really buzzfilled ride that I didn't like.

The only way to really know is to take them for a ride yourself.