First, I wouldn't worry too much about the braking system. They'll both work.
But if you insist, more Long Haul Truckers and 520s have been sold than perhaps all the others added together. Logically, there will be more of those models on the secondhand market. I suspect the REI Novara Randonee/ADV 3.1 is next in volume. The good news is that you can look for any or all of those in your size on craigslist, etc., for six months before next year's touring bike models are likely to get to the stores. So look for rim brakes in that period, buy one if you find it; if not, go buy what's available new.
Happy riding!