The 727 is the better of the two, just barely. It is a bit stronger (although I doubt you'd ever break either) and a bit shorter (though with your long wheelbase this is a moot point). It is much more efficient though! This results in better response and mileage, and generally cooler operating temps (which leads to longer life). You can bolt more transfer-cases to it without any special adapters. I beleive any Jeep x-case used from 1980 will bolt on, with the notable exception of the pre-90 NP207 and NP231s used behind manual transmissions (they have a 21-spline input shaft instead of 23-spline. You can swap in a later 23-spline shaft for the NP231 'case). The J-Truck x-case from the 80s, the NP-208, is also interchangeable and a nice way to get a part-time 'case under your rig. If you ever want to swap to a passenger-side-drop front axle, a Dana 300 will also bolt up.
This tranny was used in TONS of Chrysler and AMC vehichles and has many aftermarket parts and rebuild kits for it. Swapping a MOPAR engine (like a 318 or 360) should be pretty easy with this transmission. A MOPAR bellhousing and appropriate flexplate and torque converter can be swapped onto it. These parts are fairly cheap and easy to find in a junkyard.
They are both easy and cheap to rebuild. Get a video tape with the kit and use simple hand tools. The first time may take you an afternoon while an expirienced person may do it in an hour.