I agree with Bugsy's replies and only want to add to C:

When I want to tie a classic fly like a Catskill or something small like a midge; I like the way the thinner neck hackle fibers look. They look more delicate and enhance the appearance of certain flies. So IMHO neck hackle looks better in these situations to ME.

But I do use a ton of saddles for most other flies when I plan to look at them less and fish with them more. I just find the saddles easier to use.