Spanish Tile Roofs

I grew up with Spanish tile roofs in Arizona. But if you look closely, you will see a major difference in the construction in Segovia, Spain. The tiles are laid curve up instead of curve down as they uniformly are in Arizona. I can't guess which method is better. It seems like curve down would help remove rainwater more efficiently. It is the differences in the details that make traveling around interesting. This is the Iglesia de San Millán in Segovia, Spain.