White potatoes are not nutritious when you compare them to the more colorful varieties, such as purple and sweet potatoes. When you match them up against the more common varieties like russet and red, the difference in antioxidants isn't as profound but white potatoes still rank dead last for the category.
ORAC Source
USDA Database for the Oxygen Radical Absorbance Capacity (ORAC) of Selected Foods, Release 2 - Prepared by Nutrient Data Laboratory, Beltsville Human Nutrition Research Center (BHNRC), Agricultural Research Service (ARS), U.S. Department of Agriculture (USDA) - May 2010