I just switched from a steel frame to aluminum. The aluminum feels better racing, is more stiff, and handles better IMO, but steel is more comfortable and dampens vibrations more. My chain stay and seat stay on my steel frame were bent out from an incident, but the shop just bent them back and it was ok. Steel is stronger but heavier than aluminum and can be bent back, but basically they just overbuild aluminum so it's stronger and stiffer, but if it cracks or bends, it's finished.