I am in the process of choosing components for a custom-built touring bicycle. The bike will include mountain components (e.g., gears and derailleur), and road components (e.g., handlebars and brakes).
In terms of durability, mechanical precision, and ease of maintenance, what are the important differences between Ultegra and 105 stuff, and between XT and LX gear? I have already ruled out Durace and XTR components on the basis of price alone. My goal is to ensure that I make best use my bike budget. Will I notice a difference if I opt for the more expensive components? How can I save on components so that I can sink more money into the frame and fork?
I would especially appreciate hearing about people's experiences with Ultegra vs. 105 1) hubs and 2) STI brakes. However, any opinions about the relative merits (or disadvantages) of the different lines of components will also be appreciated.