posi traction is lsd, so it does slip and the wheels will move at different rates if the pressure plates are over by the the engine's power. the limited slip is also good for draging because if your rear wheels are pushing with the same force foward then ur gonna go nowhere but foward while in an open diff u may spin out as one tire spins faster cause u to slide the rear end in the other direction. having a locked diff is only good for off roading just like namuna stated. locking ur cars diff would not be good for racing because when u try to turn ur wheels need to move at diff speeds and ur locked diff will fight against that motion. the result would be major understeer or ur wheels will force loss of traction causing u to spin out. hope i helped someone, just some info i know
