N-S-E-W only are relevant to your hair growth. Most of my cheeks grow from N-S, but around my jawline, they start growing more E-W. Under my chin is pretty N-S, but then my neck turns E-W again. So when I shave WTG, I have to know which way my hair grows, and adjust my pass accordingly.

When I started, I just did everything N-S because that is how I used the Mach3. When I mapped my beard and not only adjusted the direction, but also the angle (my neck hairs grew at a much lower angle than the rest of my face) I had noticeably less irritation.

I tend to go one WTG pass on my whole face, then XTG on my whole face, then if I really want a nice feeling smooth (as opposed to just looking clean shaven for work) then I'll do some ATG on my cheeks.