From trig, a 1" drop at the front of a 47" long spring should rotate the axle about 1.2 degrees.
Is this a significant differrence? I am curious about the tradeoff between pinion agle and caster. Is 1.2 degrees a problem for pinion angle if you are running dual cases with a longer front d-shaft? It seems like the added caster of a no-drop hanger would be a good thing. 
1.2* of additional caster is not good. If you give the axle negative caster(towards the ground) the truck will steer under itself. If you give it more the other way, it will be slightly more stable at higher speeds, but harder to turn, and you end up with more camber under a turn.
Of course, if you were trail-only, I doubt you would notice anything.
