Hydroponic plants are known to grow 40-50% faster than soil-grown plants, and may produce 30% more yield, depending on the plant. The reasoning is that hydroponically grown plants are consistently bathed with optimal nutrients, moisture, and oxygen. so they never have to wait out a dry spell or survive a soggy environment. They aren't faced with surviving pests attacks or disease, so their energy can be focused entirely on vigorous growth.
It may make more sense to ask "do plants grow more slowly outdoors in soil?" Since hydroponically grown plants are operating in ideal situations, those actually represent the baseline performance potential of those plants. It changes the perspective when you say that plants grown on farms grow 30% slower and produce 40% less yield. From this perspective, hydroponics looks like the obvious choice.
