One of the furphies about rim brakes is their ease of setting up. Sheldon Brown has some interesting things to say about mechanical advantage and being able to get the most efficiency from cantis. Most people aren't aware of these issues and blythely adjust their brakes anyway.

There are issues with straddle cable length and others such as such as toe-in related to brake squeal. And the fundamental design parameters of various canti and V brakes can influence stopping efficiency. Just getting the pads aligned correctly on the rim can be a challenge. V brakes don't escape criticism here, either, if you run standard STI braking systems -- setting up a Travel Agent can be an interesting exercise, too.

Having just set up a disc brake on the bench... well it was just soooooo easy. The proof will be in the riding, of course.

But a critical factor not really highlighted yet in this discussion is the longevity of rims. Take the pad quality of V and canti brakes. Shimano pads are renowned for being very abrasive on rims. Koolstops have a reputation for being relatively gentle, but I have worn a Velocity Aerohead front wheel to a point of concern.

Most importantly, there are the conditions, and I am not talking about braking efficiency here -- I am talking about if you ride in wet, gritty conditions that will wear away the rim wall rapidly. A (real) advantage of disc brakes is that they rotate away from crud on the road, and are less prone to wear because they don't pick up the grit so much. Plus, you don't have horrible grey masses of fine brake dust oozing all over your rims, tyres, frame and clothing.

I am interested comments from long-term users of both types of brakes as to how long their rotors and their rims last under the respective systems in similar riding conditions.

I am not sure, also, that it is entirely fair to compare the efficiency of either brake by using tandems as the basis. No touring bike is going to be ridden with another person plus luggage on board, as well as the extra mass of the frame. The issues of overheating might be real in very very tortuous conditions, but why do not the same principles of cadence braking (on-off-on-off) apply to disc brakes?

I went with mechanical discs because of their simplicity in set-up and adjustment. I have dealt with hydraulics in other automotive arenas and they can be finickity if (a) your seals aren't totally sealed, (b) everything isn't totally (surgically) clean when servicing and (c) you don't use alcohol to clean the system (there are others, but that's a start). Above all, it's much easier to replace a broken or bent cable than it is to source a new hydraulic hose and the associated paraphenalia to connect it (which also could be read as a positive for rim brakes).

It's also worth pointing out that rim brakes are in fact disc brakes in of themselves.