[mbartell]

Open /gear differential means that the power is transferred to ONE wheel. The wheels will spin in opposite directions when you spin one.
This HELPS in turning because as you turn, one wheel will go faster than the other, because the width of the car makes the wheels move in two diffrent radii.

Locked means that you no longer have any differential action at all. Turn one wheel and the other will spin with it, and the motor will too.
Power will be transferred to both wheels at all times. Therefore there is no slip, and one wheel will loose tractoin and make the rear end slide in a turn. In a real car it would make it hell to drive, and would wear out the axle, unless you don't turn, like drag racing. In a RC car with good acceleration and light weight, it makes the rear end slide out and skid around easy.


Limited slip means that you have some differential action, but the wheels will spin in the same direction when you turn one. sometimes only one wheel will spin and turn the motor, sometimes (depending on how tight it is) it will act like a fully locked diff.
With this set up (the ball diff) you get the benefits fo both. More torque is transferred to each wheel, but in turns, you still get power to both sides, even tho the wheels are turning at diffrent speeds. You also get the added benefit of slippage. This acts like a clutch, so that the motor's RPM's go up and stay up while the wheels take a while to catch up with the rest of the drivetrain. This causes a little lag in take off, but a much more powerfull launch.

Hopefully that's not too technical, but it is correct.
Which set up you want to use is up to how you drive, and obviously what you get to work.