With all fruits and vegetables, the antioxidants are most concentrated in their skins and seeds. In the case of guava, since the skin is inedible, how much antioxidant content that's left intact is not particularly high. Unlike most fruits, where the darker varieties have higher ORAC, the white guava actually ranks about 20% higher than the red guava.
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