Setting up drive train / gearing is, imho, second only to choice in saddles, in causing more arguments about equipment. I am fond of the new Hollowtech II, with the exterior bearings. My reasoning is that since the crank / axle is one piece there you eliminate the possiblity of the crank working loose, creaking, etc. That said, all of them, square taper, ISIS, OctaLink will work, but I just think that the external BB is the best of breed.
You haven't said what kind of touring you plan on doing, I know that I like and appreciate LOW gears more than very tall gears that aren't really practical for me. I also like to have fairly small changes between gears in the back, it just make it easier to find that 'sweet spot'. My combinations are not orthodox, but they work for me.
My best advice, go to sheldonbrown.com/gears, and play with different setups till you find the one that seems to work. My LHT is set up with a 44x32x22 Crank and a 13-30 cluster. That gives me a 90 inch gear at the top, and a sub 20 at the very bottom. Furthermore I get a nice tight spacing between gears, that helps find a nice comfortable one, no matter what the terrain. That 90 inch gear is good for 25+ MPH at 90 RPM, and I've never had a situation where that has really become an issue.

I've also got a Bianchi Volpe that's geared almost the same, MTB crank with a 12-27 rear. Great for light touring, and again nice and tight.
I do have a treking crank, the 761 48x36x26, it started off on my LHT, along with an 11-32 cluster, but got changed for the current combination. It's now on my otherwise fully Ultegra equipped road bike, along with the ever popular 12-27 rear. Works great for me in that environment.
My advice, get the gearing combination that will work for your touring style, fitness level, terrain and then work backwards to find the right components.
Hope this helps....
Steve W