Well I can't honestly say that one is better than the other. I would have to suggest you try both, depending on your experience working with Polygons and/or NURBS. Both are different, but you could certainly do it with either. Basically what you feel most comfortable with, and then try moving on to using another technique.
As to online tutorials, i'm not sure how many free ones there are available. I'm sure if you look you could find some though. I bought the book, 'Learning Maya 6: Modeling' It has techniques for modeling both Polygon and NURBS heads, as well as modeling polygon and NURBS characers. It even incluedes a DVD on patch modeling a human head, which is a third technique.
Good luck

David