You can do more with a big green than a small green, if you're looking at it in a vacuum. But it's not a vacuum. Instead of green, small greens have something else in the place where the big green has - green. That something else can be fairway, rough, bunker, water, etc.
Many great holes are great, at least in part, because of a small green. The Postage Stamp at Royal Troon, the 7th at Pebble Beach, the 9th (if I'm remembering it correctly) at Congressional - all of these great holes are great BECAUSE of a small green.
Thus, while green size may be a close-to-absolute advantage when comparing greens in a vacuum, when comparing greens as to whether the green helps make the hole great, I think the answer is dependant and that variety is the spice of the life.