The best anchors are "hard anchors". Hard anchors don't move. These would include bone and teeth. Soft anchors are secondary in importance with some being better than others. Your nose is a soft anchor, but doesn't move too much and if you get your string to hit a particular spot on the nose, then it's an okay anchor.

The lips are a very movable soft anchor and not a real good choice. Combine that with a large kisser and it isn't nearly as effective as other anchors. A better hard anchor would be your cheek bone, jaw bone or a particular tooth (especially for a finger shooter). Combine that with the nose anchor and you'll have one that is easier to repeat exactly the same way on each shot.