I am a huge fan of disc brakes, but I really bristle whenever I read any person talking about the great braking power of one system or another, regardless of design. Pretty much all modern, quality brake systems have the same braking power: once the wheel is locked up, there is no additional braking power to be had. Just about every decent system out there can do this. And locking up the wheel is indicative of a loss of friction with the pavement.
The tradeoffs are in modulation (this is the implicit biggie for most people), ease of maintenance, weight, foul-weather performance, and longevity of any given aspect of the system.
Peter White is a great wheelbuilder, but he's no Gerd Schraner or Jobst Brandt; one measurement is worth 1000 opinions, even if the opinion is Peter White's. The forces involved for loaded touring with disc brakes are easily addressed with conventional wheelbuilding techniques. If you're feeling the disc love, find a wheelbuilder that thinks as you do; avoid the wheelbuilder that is mired in baseless biases. Whatever you do, read both Schraner's and Brandt's books on wheels and don't let wheelbuilders make you think that there is any kind of voodoo or obscure knowledge in wheelbuilding. The science and engineering of the bicycle wheel is quite simple (although maybe not easy) and accessible.