larger Pinion or smaller Pinion... Slower wear???

[Jahay]

ooo this is new to me... Pressure angle?

What exactly do you mean by that? Do you mean that the pinion and spur are perfectly parallel to one another rather than possibly having a bent motor mount plate causing imperfect even wear?

If thats what you are getting at , then no.. there is no angle.The wear is even and nice all the way around the pinion.