In general, aluminum will be a stiffer ride thus also being less forgiving. Steel is more forgiving and will flex some thus creating a more comfortable ride. Steel is heavier than aluminum, but not a drastic amount. As mentioned, the bikes in the Regal link are hi-tensile steel and at $400+ not a very good deal. You can get chromoly steel frame and fork bikes in the $300 price which IMO would be better.