My aluminum bike was heavier than my steel bike.
To get strength, aluminum tubes tend to have thicker walls and be larger diameter; which means they have to use more metal.
Generally they seem to pretty much even out steel vs aluminum, and I'd pay more attention to the components for weight.
Some people really have a preference as far as frame material, some can't tell the difference.
Frame material probably doesn't matter much in the great scheme of the universe, as long as you get on ride, ride, ride!
"If Americans want to live the American Dream, they should go to Denmark." - Richard Wilkinson