Natural vs. Synthetic Vitamin C

I have had two people tell me recently that they have heard that Ascobic Acid (that I use in my food bars and powders) is not as good as natural sources of vitamin C. While I agree with “natural is better than synthetic” as a principle and have seen claims, assertations and opinions to that effect but the below is the only reference I have seen to studies testing the hypothesis. If you come across any clinical studies, please let me know.
Natural and synthetic L-ascorbic acid are chemically identical, and there are no known differences in their biological activity. The possibility that the bioavailability of L-ascorbic acid from natural sources might differ from that of synthetic ascorbic acid was investigated in at least two human studies, and no clinically significant differences were observed. A study of 12 males (6 smokers and 6 nonsmokers) found the bioavailability of synthetic ascorbic acid (powder administered in water) to be slightly superior to that of orange juice, based on blood levels of ascorbic acid, and not different based on ascorbic acid in leukocytes (white blood cells) (1). A study in 68 male nonsmokers found that ascorbic acid consumed in cooked broccoli, orange juice, orange slices, and as synthetic ascorbic acid tablets are equally bioavailable, as measured by plasma ascorbic acid levels (2, 3).
http://lpi.oregonstate.edu/mic/vitamins/vitamin-C/supplemental-forms