Who's right? Depends. If you can achieve the desired pinion angle AND the desired equal and opposite operating angles of the front and rear u-joints at the same time, congratulations. To do so requires the engine/ trans assembly and the rear end to be at the correct heights, angles, and distance apart. Usually only achieved on a car built from scratch. For example, if the tail shaft is angled down from front to rear and the front u-joint is lower than the rear u-joint, you can't make the pinion and the tail shaft parallel without having the pinion angle go positive which is never ok. Pinion angle is most important and can't be made wrong in order to get the pinion parallel with the engine/transmission.