Hey Jun, you've asked a heck of a good question. In comparing Hydroponic growing with soil growing, you have to set the amount of care used with each type of growing.
Soil:
If one were to put a plant into barren, rocky soil and give it no water or
nutrients, then the plant would die rapidly. That's the bottom of the soil scale.
If however, you provide the plant with rich, aerated soil that has a bounty of usable nutrients and plentiful pH corrected water, you've given the plant all you can in soil and it will grow at an awesome rate. That's the top of the soil scale.
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Hydroponic:
If you were to stick a plant into a bucket full of gravel with chlorinated tap water at a pH of 8.0, never give it any nutrients and used a 25 watt incandescent light over the plants as their only source of light, then the plant would die rapidly. That's the bottom of the Hydroponic scale.
If instead, you use top of the line equipment, the outdoor sun when available and proper plant lighting indoors when the sun isn't available, the best nutrients available for the plant you're growing at the exact rate that is perfect for that particular plant, saturate your root zone with oxygen and are careful with pest control, then that would be the top of the Hydroponic scale.
My point is, that regardless of either soil or hydroponic growing, there will be only the results that are obtained by the level of care you give your crops.
Now to answer your first question; IF all care is given, and both types of growing are maximized to the extent possible, and both systems are provided with thier optimum variables, then the hydroponic systems will outperform the soil with notable harvest increases, with the ratio of increase dependant on the type of
hydroponic system used.
If one were to give maximum care to an
aeroponic hydroponic system, then it would out-perform any other form of growing known today, given identical care with it's soil counterpart or even it's hydroponic counterpart.
So, in final answer, if you used an aeroponic system and maximized it's capability, then it would out-perform any other type of growing you did.
(Sorry for being long-winded, but that was a *Huge* question.)