Steelies are way heavier. MPG and performance were both hindered on mine...measurably. I'd say it hit me for about 1mpg and about .2 seconds 0-60 (I realize some people could care less about the 2nd one). Pros and cons to both I guess, but I ended up returning my steelies to Discount if that tells you anything and went back to the original alloys. And yes, I wheel(ed) my rig in the AZ desert (at the time).
Now I just encourage people to paint their existing alloys. New look, same performance.