There are advantages and disadvantages on both sides of the soil debate, but the highly controlled environment of soil-less hydroponics is a significant advantage to some growers. Of course, highly controlled also correlates to a more complex endeavor, since hydroponics growers need to spend at least some time reproducing the beneficial effects of soil within the more sterile environment. The natural pH buffers present in soil are a prime example - agricultural fields typically only need to have soil amended for pH at the beginning of the growth system, if then. Hydroponics growers need to test the pH of their nutrient water often on a daily basis, since the natural buffering action of soil is absent.
One oft-cited disadvantage to hydroponics is the price of setting up a good system and the cost of operating it. While it's true that setting up a fully automated modern system can be very pricey, the long-term profit can exceed that of traditional farm-grown vegetables. High yields, high quality produce, and reduced costs associated with pests, drought, and crop diseases all tip the scales, sometimes significantly, in favor of hydroponics. Of course, there are probably always going to be some crops that are best suited to more traditional farming practices, like corn, because of the amount of space it requires compared to its yield. Of course, dwarf fruit trees thrive in hydroponics setups - perhaps someday there will be high-producing dwarf corn plants perfect for the discerning palate.
