I've never had a chance to ride a steel bike (because no one has my size). However, I've ridden two carbon bikes. One was a very, very smooth ride, almost disconcertingly so, because it was hard to "feel" my way around corners and so on. The other wasn't quite as bad, but it was a shorter ride.

I think steel bikes tend to be "all-rounder" bikes, like Surly's offerings. They're not necessarily quick, but they're comfortable. If you want to go fast, then look more closely at carbon.