I'll admit to not reading this whole thread, but I really like the Truetrac in the rear of my truck. I'm still open in my front D60, someday it will get a selectable front. The truetrac gets a bad rap from hardcore wheelers, but it really does work well as long as both wheels are on the ground, especially on a street driven rig, or one that sees a lot of snow/ice. The drag the brakes trick works to get traction to both sides in the scenario when a wheel is in the air. I've had a Detroit in the back of a manual trans long bed pickup before and it made for some very scary winter driving at times.
Best Options:
If you have the money for it: Selectables front and back.
Truck that sees a lot of street miles in places that get real winters: Truetrac Rear or other limited slip. Front: Selectable, Truetrac front would be decent as well.
For a rig that only sees trail duty, Detroits front and back, or Detroit rear, selectable front.