Well Just dropping DLI which i had to scroll to the google bottom which is correlated to PPFD tells me you should have a PHD.DLI primarily. The plant processes change from photosynthesis to the Calvin cycle. There is sooo much to it that your best off researching them if you really want to learn about it. It also ties in to spectrums and ratio changes in them, nutrients, carbon fixation. Just way to much to try to go through and I don't have a PhD in any of it.. high-school drop out here.
But a 2 hr difference for our purposes generally will be most impact full on the DLI.