No diff...
As long as they are striaght and spin true.
I do all mine the same way just to be safe.
(they look cooler that way too. almost like the arrow makeer knew what he was doing)

If I used a 2-blade, I'd have it horizontal so it couldn't blow off my rest as easy.
If you shoot instinct, you might also want a 2-blade horizontal for an easier to see visual reference point.