Fresh, Frozen, Canned

Which is better? I debate this with myself quite often at the grocery store. I've heard that frozen and/or canned vegetables might have more nutrients than their "fresh" counterparts because the former are processed as soon as their picked whereas the later might take some time to appear on shelves. With respect to frozen vs. canned, canned vegetables can lose some of their Vitamin C in the heating process during heating, but they are preservative-free. However, as one might imagine, "fresh from the garden" vegetables are the healthiest (and probably tastiest) of all. It's just important not to overcook any vegetables, as this causes them to lose some of their nutritional content.