Does light on the buds contribute significantly or just the light that hits the leaves?
I haven't researched how much direct light effects bud growth, but through personal experience I have noticed more growth to the lower 1/3rd with direct light. Not much more, just a matter of an extra 1/8oz or so of popcorn in the hash pile. This can be achieved by a few cfl's under the canopy coupled with proper branch training to spread the canopy open and allow light to penetrate to lower bud sites.
But on the other hand my colas are much smaller when I lose too many fan leafs to diseases or deficiencies. The fully grown leafs are basically sugar factories, requiring very little maintenance from the plant to keep alive. And if the plant is deficient in any mobile nutrient, it takes it from the lower leafs, defoliating itself as needed, and sends the deficient nutrient up the shoot, which during flowering are the buds!
If you ever feel froggy, take 2 clones from mama, and when buds first emerge heavily defoliate one and just train the other and record the outcome. And if you do, please share it with the community! But I'd have to say, based on what I've seen in my experiences, the one left to it's devices will outperform the other overall.
Good luck, and stay curious, my friend.