Chillers, in general, are better than most other cooling systems due to one simple fact - consistency. If you're using a chiller, then you hardly have to worry about constant fluctuations in the temperature. It's also easier to change the temperature at will without having to wait for hours like other mediums. However, chillers are super expensive (at least the good quality ones) & there are lots of hidden costs in the maintenance & upkeep. Hence, if budget's an issue, it's not that great of an idea to use a chiller for coral or other varieties of reef tanks.