FYI, here's the differences between the (2) systems off Jeep.com
http://www.jeep.com/en/4x4/systems_by_vehicle/
Quote:
Selec-Trac II®
Selec-Trac II supports the new MP 3022 two-speed, full-time active “on-demand” four-wheel drive transfer case. When driving in 4WD Auto mode, the transfer case clutch pack detects wheel slip and applies increased or decreased torque between the front and rear axles based on real-time driving conditions, thus optimizing traction. Under the right conditions, the vehicle can be driven by just one wheel. For added capability when traversing steep grades, rough terrain, or extremely poor tractions surfaces, the transfer case includes a 4WD Low mode. Electronic shifting between 4WD Auto and 4WD is accomplished via a console-mounted switch. A 2WD mode is also provided for some markets.
Command-Trac II®
Command-Trac II® supports the new MP 1522 two-speed, part-time four-wheel drive transfer case, featuring smooth operation, shift-on-the-fly capability, and improved NVH control compared to systems with mechanical linkage. 2WD High is the usual driving mode, with the front driveline disengaged from the transfer case and power directed to the rear wheels. Selecting 4WD Lock via the electronic, console-mounted switch locks the front and rear driveshafts together; the two then rotate at the same speed and provide a 50 front/50 rear torque split, providing better traction on slippery surfaces. This transfer case allows for 2WD, 4WD high-range and low-range as well as neutral.