It as simple as a size difference or is there something else? I have my opinion but I would like to hear everyone else's on the matter.
its in my opinion that if the pinion gear were the size of a pop can,, then the torque from a 3.8 out strip it out due to torque. Somethings gotta give when you romp the gass so a larger pinion helps to absorb some future growth in the power plant.