Photosynthesis uses energy in the red part of the visible spectrum. That's why they look green. They do not absorb the green light, they reflect it.

Plants store their solar energy in a hydrogen-carbon bond for storage. To compare a plant with a solar panel and LED you need to also include the storage technology, which is usually batteries. Because plants do not as a rule glow brightly, a more apt comparison would involve, say, a locomotion system. Comparing the efficiency of, perhaps, a car that drives at night powered by a solar/battery system vs. a plant/combustion system. It would be an interesting experiement.