I guess it's a trade-off between correct CV joint angles and ground clearance. If your torsion bars are only cranked about 3" or so, dropping the diff 1.5" lets you keep some clearance and mostly correct the joint angle. I think if you crank them all the way to 4" you might want a greater diff drop to correct for that, as even with the diff drop brackets, your angle is off by 2.5". I guess that's why you're still going through CV boots, as your axles sit at nearly the same angle as mine without the diff drop.