I'm guessing the differences would be noticeable as the lighter bikes would feel different from the heavier ones. If they were all the same weight, the differences in ride quality would be subtle and if the tires were wide enough, very hard to discern at all.

And why would this matter to the OP or anyone else at all? If carbon fiber was truly the sweetest ride on earth, would you trade in your lugged steel classics and buy a new Giant?