Run white letters out if you have 60 series or higher tires. I have 15 inch 65 series on Magnum 500's letters out.
If you run a low profile tire, the letters out looks funny or may not even be an option.
Ohhh, and you guys can clean your white letters with White Lightening (available at Home Depot). It is the best cleaner I have found for doing the lettering.