They're actually about the same.
75% uninteresting/poorly drawn shit, 23% interesting in some way or borderline save-worthy (usually a good concept but suffers from flawed art), 2% save worthy. (I originally went with 5% save worthy, but it'd be a lie to say that I save 1 out of every 20 Nanoha fanart pics that I see posted)
And Fate has the most fanart by far, so she also has the highest amount of save-worthy fanart. (of course, since this is a Teana thread and Teana's awesome, I'll stay on topic)