Generations of Component Groupsets (e.g. Older X0 vs. Newer X0)
So I'm looking at used bikes, and I notice that some bikes are decked out with XTR and X0 components. However, they don't look like the newest components offered by SRAM and Shimano. Therefore, it's easy to conclude that both companies are continually improving and releasing new versions.
I am wondering whether there is a significant difference in weight and performance across generations of each groupset tier (e.g. older X0 vs newer X0), and whether newer X7 components (or the like) are better than older X0 components.
Anyone have any insight on this topic?
(I'm trying to evaluate the value of a high-end 2004/2005 used bike decked out in X0/XTR components.)