How thin can you slice the baloney?

Shimano has 5 groups of road components. They all do the same thing and they're all functional. As you move up the food chain the components get a little bit lighter in weight, a little bit smoother operating, and a little bit more nicely finished. The price, on the other hand, goes up exponentially. My rule of thumb has long been that I can sense a difference if I move up or down 2 group sets but not if I move up or down only one group.

That's a long way around saying that, if it was my bike, I'd go for the titanium frame.