Personally the strongest brakes I have ever ridden are magura hydro rim brakes, the ones on my trials bike are probably 10 years old and have had nothing but a pad change.

I have owned hydro and mech discs, canti's and v-brakes.

I honestly feel the v-brakes I have had always had more power than any of the discs I have owned (bb7, juicy, hayes 9, tektro mech) unless it was nasty out, especially when it was 25deg and wet, standing water would splash onto the rims and it would take a little longer for them to grab, but not a big deal if you are conscious about it.

If I was building a dedicated around the world tour'er I would use bb-7's, they are unbelievably easy to set up and work on and have an outstanding track record for reliability, I would just carry a few extra sets of pads since they are so small. They are not hard at all to work on if you understand the theory, they actually set up much easier than rim brakes. The chances of a rotor getting bent are there but I have straightened some pretty horribly bent rotors with good results but if you take care like vik said when shipping the bike you should not have issues.

Hydro discs in theory are the simplest disc brakes out there, a few pistons, brake lines and some fluid. The only problem on a touring bike for out of the country is that lines can be hard to find and many take a special kit to be able to bleed them. I would save these for the mtb.

Rim brakes are also very proven and have a ton of stopping power as well, and with the right pads stop well when it is wet too. The only problem is rim wear, I have had one rim blow out a sidewall and another get concaved enough that I should have replaced it, it was always in the back of my mind on long downhills.

I think it comes down to, are you comfortable with setting up disc brakes, or mechanically inclined enough to learn? If so I think bb-7's are tough to top although when set up wrong they will feel like poo. If you are not comfortable and do not pick up mechanical things well then keeping with rim brakes might be your best option, either way you can not go wrong, both will serve you well if properly set up.