If I had to choose, I'd go with the pinion snubber. What you are trying to do with either is limit the amount the leaf springs wrap up under hard acceleration. As you accelerate the pinion will try to climb the ring gear. Obviously it cant so the energy is tranfered through the diff, down the axles & then to the wheels. The energy is then transfered back through the whole rear axle assy & it tries to twist itself free. This causes the leaf springs to twist to a point & then release causing the chassis to unload & cause spin & hop. A snubber or traction bars limit the movement of the axle housing to a point before the springs wrap up & unload. Traction bars do it at the point of the springs individually, while the snubber does it centrally at the middle of the axle housing. I'd rather do it in the center as depending on the weight transfer you may not get both traction bars working at the same rate.