You need to look at the whole package inc. geometry, wheels, type of steel etc. A well designed bike can be made of CF, Al, Steel or Ti. Unless the 2 bikes you compared have the very exact geometry, contact points, wheels, tires etc. all the differences you felt could have been things outside frame material. Just changing tire pressure changes comfort and response a lot.

Steel isn't inherently comfortable, look at Walmart. And the one person's "comfortable" is the other person's "unresponsive" or other property of the very same bike.

Butting is just an attempt to optimize material thickness at different locations. A very crude attempt compared to what CF allows.