I have two Treks, a 1995 steel 730 and a 2007 aluminum 7.2 FX and I am riding them concurrently to decide on which frame to upgrade some components. The steel bike has slightly better components and by just lifting each, it's the lighter of the two bikes. Having said that, the aluminum bike feels more responsive and faster.

There are numerous other factors like geometry of the two bikes (close but not exact), crankarm stiffness & length and probably other factors I'm not aware of. I've ridden each bike with the others' tires & wheelset and regardless of what combo I use, my experience supports the "common wisdom" that a steel bike rides more comfortably while an aluminum bike rides more harshly. Also, the aluminum bike is more responsive to acceleration, even though I think it's the heavier of the two.

Don't take those two observations too negatively. The aluminum bike rides fine and the steel bike accelerates fine, there is just a discernible difference between the two.