The problem faced by tourists but not race or MTB riders is integration of the brake with all the other stuff: racks, fenders, lights etc.
Disc brakes can integrate well if they are placed correctly, ideally on the rear chainstay and at the front on the driveside, leading edge (ie opposite to a normal front disc). This gets stuff out of the way of fenders and reverses the forces on the axle so braking forces the axle into (not out of) the dropout.

Disc brake units are not designed for chainstay mounting so the cable run is at the wrong angle. As this mount becomes more common, I imagine that Avid will make a road version for this location.

Is there any debate regarding ISO vs post mount?
Forks need to be stiffer on a disc-equipped bike; how does that affect comfort?
I use Shimano centrelock disks but for travel, I think 6-bolt are better, you dont need a vice or long wrench to replace them.
Pads are easy to carry and can be quite cheap. In the UK we have a "no-brand" brand called Superstar who sell pads from the same Chinese factories as everyone else, at a fraction of the price of Shimano/Avid.

My canti setep drives me to distraction. Nothing plays well together and I cant buy the bits that I need to make it work. Cantis are going out of fashion and sooner or later, will drop out of the market altogether.