what does it mean when a piece of equipment is jacketed?
Usually it means the tank is equipped with a cooling surface. The best cooling jacket has a dimpled appearance (usually smooth on inside surface). They are more expensive to build. They are usually insulated as well to allow the tank to maintain a cooled temperature.
A single walled tank is less expensive, but the only way you can keep it cool is by controlling the environment it is in...meaning a cold box. This is much less efficient at maintaining beer at a cold temp. This is sometimes used at brewpubs, and even large (the largest) breweries.
I would go with jacketed tanks. Much easier to control the product temperature.
Temperature is a very important control parameter for a brewery that wants to make a high quality beer.