Water Chillers:

Water-Cooled Chillers can use plant water or city/well water in their cooling process and have cooling towers to dissipate heat.

Water-Cooled Chillers absorb heat and transfer it to a secondary water tower pond, river, etc. They are the preferred choice in larger applications. There disadvantage over air-cooled units is that they require occasional cleaning where mineral deposits are an issue. When mineral deposits build up, a unit can become less efficient.

Air Cooled Chillers:

Air-Cooled Portable Chillers rely on ambient air to dissipate heat to.
 

Air-Cooled units are advantageous in the fact that they don't require a cooler tower and condenser pump. Since the heat is just release into near by air. These coolers suit areas that have the air space to release heat to.