And even that juice has fewer vitamins, because the temperatures involved in canning destroy some of them (vitamin C, for example). Plus a lot of canned vegetables are processed with preservatives and large amounts of sodium.Yes, basically because canned Vegs are not fully cooked from my understanding. They maintain more of the nutrition/vitamins because they haven't been cooked off.
Edit: I was backwards, sorry. Frozen are blanched and the Vegs keep more vitamins. Canned Vegs have most of their vitamins within the juice. Thanks for making me look.
The only vegetable I know of that benefits from canning is tomatoes, because the processing increases the bioavailability of lycopene.