No nobody knows. I believe that you will see quicker, faster growth the longer the lights are on, but just through qualitative evidence it seems that plants will end up doing better in flower if there is some dark period. I used to do 24/0 all the time, now I tend to do 4-6 hours of dark and it helps give a cool off period as well as saving on elec.
I still would like to see a "study" or experiment done on this. It is too bad that the stakes are high and we can't just have two veg rooms going just to see what clones do better in the long run. If I had room I would do it, just because I am sick of the constant debate and bickering about it.
Unfortunately I don't even have room for a normal grow let alone something experimental.
Peace y'all,
PP