I just know that I prefer metal to carbon frames. Just my preference. These days, though, steel roadie frames are getting to be almost as light as ti or aluminum without sacrificing stiffness where you want it. My SS, MTB and roadie are all steel. The fixie is alu, just because it's my old road bike and still wanted me to ride it. It's really gotten to where the differences beween the weight of materials is almost negligable at the high end.