If you really want to get technical about it, consider what you're trying to imitate. I'm a believer in different types of hair, or feathers, in the same jig. If you consider a craw, some parts move and some don't. So use Bucktail for the non movable parts, and marabou, rabbit, fox for the moveable parts. I always go sparser rather than fuller on all my hair jigs.
Believe it or not, most of the time I just get lazy and tie arctic fox only.