For the street I don't think that you would want a Locker. Making turns on the street under power would cause the rear to bounce because the wheels will be turning at the same speed but the distance each wheel travels will be different. This would be good for drags in a straight line.
Posi traction or Limited slip are the same. By limiting the velocity difference between a pair of driven wheels, useful torque can be transmitted as long as there is some friction available on at least one of the wheels. When traveling in a straight line, where one wheel starts to slip (and spin faster than the wheel with traction), torque is reduced to the slipping wheel and provided to the slower wheel. In the case when the vehicle is turning and neither wheel is slipping, the inside wheel will be turning slower than the outside wheel. In this case the inside wheel will receive more torque than the outside wheel, which can result in understeer.
With the Truetrac it operates as a standard or open differential under normal driving conditions which allows one wheel to spin faster or slower as necessary. When a wheel encounters a loss of traction the gear separation forces take effect and transfer torque to the high-traction wheel.
I went with the True Trac and like it a lot. No issues so far running 3.89 rear. Here is a good explanation on how they work.