Aluminum will be stronger and stiffer for any given weight than a steel frame (better quality steels can close the gap though)
That's why bridges are made of steel and planes are made out of aluminum.
Now ride quality is based on tubing diameter and the amount of flex it has. Aluminum bikes can't tolerate flex like steel can therefore they are designed not to flex too much.
My steel bike rides better on rough rodes (small diameter lugged steel frame), but my large diameter Aluminum framed bike goes up hills better when I'm climbing out of the saddle.
Originally Posted by jo5iah
material is far subordinate to the maker - and that doesn't mean it needs some big fat lettering on the side.
Yeah, this is true.