Quote - Don't bother making a separate material zone for lips. Any lipstick or gloss effect should be driven by a mask. When you assign the lips a different material and don't use a mask with soft anti-aliased edges, any lipstick effect looks fake. It's important to blend the lips with the face. So in my VSS shader, I design the face shader as one thing and I never put a different shader on the lips.

Personally, I'd prefer a material zone for the lips.  It provides the user with more options in case they are not using VSS.