Hard to compare for me as my carbon bike is a TT bike so its going to feel very different to my alu road bikes simply due to the geometry. But I'd say in my experience (comparing a Cannondale CAAD9, a Cannondale Slice, and a Cinelli Vigorelli) that the carbon bike feels stiffer but at the same time less "harsh". The TT bike is heavier than the road bikes though despite being carbon.
But then again these sensations, might be more down to the geometry than the frame material, the Slice is designed to be a long distance triathlon bike and thus is designed for fast straight line speeds, whilst having some built in comfort features to save you enough that you are fresh enough to be able to run a marathon after a 112 mile time trial.
In addition, comparing materials blindly is a bit pointless.