Here is another way to understand what is going on:
VSC:
PURPOSE: Helps correct skids while cornering too fast at highway speeds.
HOW DETECTED: Steering angle doesn't match direction vehicle is going.
INTERVENTION: Reduces engine power, brakes one or two wheels.
PROBLEMS: Can cut power just when you need it! In deep snow, sand, or mud, turn it off.
ABS:
PURPOSE: Avoid skid while braking.
HOW DETECTED: While braking, one wheel is turning slower than the others.
INTERVENTION: Reduces braking on that wheel.
COMMENTS: A lifesaver! In a panic stop, even on snow or ice,, you should stomp the brakes hard, and let the ABS control the stop.
ATRAC:
PURPOSE: Prevent wheels spin while accelerating, especially in low range.
INTERVENTION: Applies brake to the wheel that is spinning.
PROBLEMS: Can get confused. Works best in low gear, low range. Keep a slow steady rpm.
COMMENTS: Works great! For most wheelers it is as good or better than lockers, as it it is always available, doesn't bind the steering, etc.
CENTER TORSEN DIFF:
PURPOSE: Allows 4wd to be used on dry pavement without binding, wheel scuffing, or breakage. Sends more torque to the axle that has traction.
INTERVENTION: Differential effect allows turns without binding. Torque sensing distributes torque where needed. Can be locked if needed.
COMMENTS: All 4wd vehicles should have this! All 4th gens have this, but not the more recent models. (All Limited Editions have it) Use 4wd whenever and wherever. Less wheelspin. If I ever buy a new 4runner, I'll get a Limited just to have this feature!
LOCKING THE CENTER DIFF: Rarely needed. IMHO, only needed if you need extra traction to start from stopped. Also needed to back down from a failed steep hill climb. Otherwise, let the torque sensing distribute the torque.