Grape juice vs. orange juice, which is better for you? Well both have high amounts of sugar, so they both lose in that category. Though when it comes to antioxidants, the amount in grape juice is significantly more - about 3 times higher - than orange juice. This is because of the blue and purple pigments in concord, which contain polyphenols, resveratrol, and other phytonutrients which aren't found in every fruit and vegetable (or found but in lower amounts). Ideally though, consuming fresh is better for your glycemic impact - since juice removes all the fibers, it means the sugars in fruits are absorbed immediately rather than over time (and hence, are less likely to cause a huge spike in blood sugar).
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