There is a difference between the frames (marginal advantage ) and the components (Shimano AX especially). Shimanos gruppo introduced a comprehensive approach to a design formula which also included a primitive click shift in the rear derailleur, rear entry brake levers ( no smut here) now industry standard, freehubs instead of freewheels, etc. See vol 2, On the Wheel for a component by component analysis of the engineering and design issues. Alan Bernstein NYC