Okay, I'm starting to really get this but something new:
In model space, call outs are small and spaced very far from the arrowhead, looks strange and will probably confuse others if they are not familiar.
In paper space, call outs are the right size and through the view port I can adjust them so they look great. This makes them even weirder in model space.
If I adjust them in model space, they overlap in paper space.