It's the construction that matters more than the materials usually. Aluminum frames/forks can be flexy/noodly or stiff as a brick, or anything in between. Same goes for CF and steel. Changing the build process, tubing thickness/shape, etc... all have a huge effect. While CF may deaden some of the vibrations that Al won't, I don't find those to be an issue unless you're on a 30+ mile ride. For average commuting distance I don't think I'd even notice. I'd take big tires on an aluminum fork over skinny tires on a CF fork any day of the week.