I have four road and cross bikes in my stable. One carbon, one aluminum/carbon, one aluminum, and one steel. All of them ride smoothly.

I have one bike that's on its way to Craigs list -- a way too-stiff aluminum bike that I replaced with the steel bike.

The material that a frame is made from is not the sole determinant of how it rides. You simply can't generalize fragility/durability/stiffness/noodliness/plushness/harshness/etc.ness based solely on material.