Petronics uses a hall effect transistor as a sensor. It picks up magnetic pulses from the rotating ring that is slid down on the distributor shaft underneath the rotor in place of the points. The only way this can fail is if the hall effect transistor fails. The other brands use a rotating disk with little slots cut into it. The sensor is an LED/photo cell. If enough dirt builds up on the surface of the sensor or if it closes up or changes the " shape " of the slots, you will start having problems. They are both very good ways to elimate the need for points, will last forever in most cases, and will certainly provide a more reliable and evenly shaped pulse to trigger a high voltage spark from the coil than the original set of points. I like the concept of the petronics not ever being able to be bothered by dirt / foreign matter buildup. But since they both work so well, it is just a theroy. You can chose the one you want without much to be concerned about. IMHO .... Almost forgot, the petronics has one failure mode, the hall effect transistor fails. The other has three failure modes, the slots can fill up with dirt, the LED can fail, and the photo cell can fail. I guess that is the real case for using the petronics unit.