All did better in two coats. Fingerprints, spatters, even dust and grime in the air can easily stain some paints, especially in high traffic areas. A good paint should be easy to clean with a sponge and spray cleaner. As a rule, flat paints will hold a stain more tenaciously than low-luster paints, and so will be harder to clean. Mildew is a common problem in bathrooms and kitchens, but it can affect any warm, humid room, especially on a cold exterior wall.
Some paints contain mildewcides to prevent fresh growths of mildew from marring their surface.