The rap on aluminum is that it rides harsh. It's a simplistic view though. I have an all aluminum Trek 1200c that has a relaxed geometry and is quite comfortable. I’ve also ridden a Cannondale race bike and it beat the hell out of me. Weight of the rider matters too as the heavy guy will not be as bothered by Aluminum as a lightweight.
I think aluminum is getting a bad rap because it’s the cheapest material to produce and its human nature to assume the more exotic materials is better. Steel used to be old fashioned and no one wanted it. Now it has made a comeback so truly you should determine what you want out of a bike, make a list of bikes no matter what the material, and then ride them all.