I'll make it easy for you - get the Surly LHT - excellent design and good value. It's made in Taiwan by Maxway, who makes many fine (Rivendell!) bike frames. If you want discs brakes get the Disc Trucker - exactly the same as LHT but disc instead of rim brakes. Both the LHT and DT are made with long (46cm) chainstays so your heels don't strike panniers as you pedal. Many so-called "touring" bikes skimp on this important detail to save $5 in manufacturing cost. The LHT/DT top tube is larger diameter and thicker-walled than many competitors, which translates to improved load handling and riding stability. Most every detail on the LHT/DT is well though out and implemented. If you are looking at complete Surly bikes, know that the components are well chosen for performance and value.

If you can build your own bike you might prefer to customize componentry, maybe even saving money over the complete bike (although hasty first-timers often end up spending more). MTB fans often choose the DIY route to build LHTs with flat bar/mtb components instead of the traditional drop handlebar. Framesets are as low as $399 shipped in the USA.

I own a LHT and a DT. The brakes on the DT are better (better modulation/control, more power, and they work in the rain), but this comes at a cost of increased weight. A DT weighs 2.0-2.5 pounds more than a same size, identically-equipped LHT due to heavier frame/fork brake mounts and the extra weight of disc calipers/rotors and longer cable/housing runs. Cantilever aficionados will correctly warn that disc brake rotors are prone to bending from improper handling/transport/maintenance. However, rotors can be easily unbent and trued in the field with only a small adjustable wrench, good lighting and some patience for the repair.

If you prefer mtb-style flat bars over drop bars, then an excellent brake compromise is V brakes on a LHT. Vee brakes usually offer better braking than cantis without the weight penalty of discs. Vs can also be fit to drop bars but either special levers or cable-pull adapters are required for compatibility.

Like others, I also recommend a 26" wheeled bike if you plan to tour outside North America, due to the relative scarcity of 700c wheel/rims/tires/tubes in other parts of the world. 26" wheels are easier to fit to smaller frame sizes without compromising geometry or toe-fender clearance. Surly LHT/DT are offered in 26" versions for all sizes.