There are a few 'advantages' to growing plants via hydroponics. It is mostly just a way to grow plants in a different environment (indoors, or in a non-native environment). Just like growing vegetables in a greenhouse wouldn't per se be 'better' than growing them in a field. There are advantages to both: a greenhouse allows you to grow things that aren't naturally suited to your environment, whereas a field would allow you to a much larger quantity of plants per cost. Hydroponic is just another way to suit a person's tastes/needs in a growing environment.
Here are a few things hydroponics can accomplish or accomplish easier than other methods:
- Control over nutrient uptake (can adjust in water supply)
- Grow plants indoors without the use of natural light
- No hassle with soil setup and testing
- Generally weed free environment (if done indoors)
- More plants can fit into a smaller space
- Easier harvesting
There is some debate as to growth speed and nutrient retention. Generally, grow speed is faster in a hydroponic system. This is somewhat due to the increased nutrients supplied in a water supply and the roots of a plant can directly absorb them. However, in a soil based system, if a fertilizer or nutrient is applied regularly it can have the same effect so just because the system is hydroponic in nature, doesn't necessarily mean your yield will always be more.
Here are a few disadvantages over more conventional growing methods:
- No soil buffer. If the hydroponics system fails, plants will die much faster.
- Increased energy cost (if using growth lights and air pumps)
- Water-based pathogens can be easily introduced
- More complex handling/tracking of nutrient solutions
- Much higher cost to start up system compared to traditional methods (need to purchase nutrients and supplements to keep plants alive)
Here is a decent hydroponics system just to give anyone an idea of start-up cost. There are many DIY tutorials out there as well.
Just a note: hydroponics isn't necessarily growing plants in water, a substrate may still used (such as perlite or fired clay pellets). The difference is that the plant is not absorbing any nutrients from the substrate, its getting it all from the water.