If I plan to tour I want as many functional bells and whistles as possible. Most notably a third bottle cage, fork lowrider mounts, and canti brakes. I've toured a number of times on my Specialized Expedition and found it can have shimmy issues unless specifically loaded extra heavily in the front with no handlebar bag. It is very similar to the Miyata 1000 but the splined tubing of the Miyata may make that a bit stiffer. If loaded properly it is very comfortable and also a nice ride unloaded. Due to those flex issues I bought a 1987 Schwinn Voyageur which I found to have super stability no matter how it is loaded. Slightly heavier than the Expedition but still a bike I enjoy riding unloaded. I left the Voyageur with 27" wheels and I think that makes it seem to roll fast enough I don't notice the weight. My most recent purchase is a 1990 Cannondale ST400. This is a year they had cantilever brakes. I really love this bike for general riding and it is much stiffer than the other two without sacrificing much in ride comfort. I hope to give it a try loaded this spring and based on the stiffness I expect it to be very stable. It is definitely the lighter of the 3 and best suited for an all around bike.

As other's have mentioned the type of touring you expect to do can dictacte your best option but I can definitely recommend getting something you can solidly mount a front rack on. Splitting your load between front and back will definitley improve the stability.