When the test references "without peel" what that means is that the peel was discarded for the purple of measuring the fruits total antioxidant content (since people do not normally consume the peel, with the exception as perhaps a spice). How much more antioxidants are in raw lemons versus lemon juice? Only about 10% more. So with either, it's good way to add a bit of nutrition to your water or make to a healthy lemonade.
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