Without lockers in front and back, you don't really have 4WD.....The differential will transfer the power to the wheel that turn the easiest.

 

While that is true, I believe that the manufactures call it 2 wheel drive because power is available to only 2 wheels, and 4wheel drive because it has power available to all 4 wheels. It is the action of the differential's in each axle, that determines which wheel gets the power.

The advantage of the locker is when it stops the differential from sending the power to the wheel with the least resistance (the one hanging in the air or spinning in the mud) and sends it to both wheels on that axle equally, so the wheel that still has traction can still move the vehicle in the desired direction, thus the advantage for off road.

 

4WD is good for getting you stuck deeper, farther away from home.

Never assume that you will get better traction with 4WD. What you get is better acceleration against a low friction surface. It won't help you slow down and it won't help you corner. And that's why I get to pull people out of the ditch during the winter.