Well I haven't done the experiments myself, but I have read it enough places that I take it as a fact that light degrades THC. If you believe that information then you don't have to be a rocket scientist to figure out that the best time to harvest is after a dark cycle.

If the thing about sugars going into the roots is true as well then that's one additional reason to harvest after a dark cycle. It's the first I've heard of it, and it reminds me of the crap you read about boiling roots or hanging plants upside down, so I am skeptical. It doesn't sound too far-fetched though. Are sugars in the plant mobile?