Based on what the restaurant building is designed as, your choices would range from central air conditioner, split air conditioner, PTACs, or even portable air conditioners. A restaurant would need a powerful air conditioner due to the ongoing heat produce in the kitchen. Most of the restaurants already have ductwork done and hence it would be easy to just buy a more energy efficient central ac in case of replacement. I mean the goal here is to save money, right. If you are looking for a heating and cooling solution for you sitting area, it would depend on what your needs are. I personally suggest a split air conditioner as it would look more aesthetic and can provide a decor look to room. Have you heard about the picture frame air handlers from LG? They basically look like a picture frame with an air handler hidden behind it. If you install a PTAC system, it might help with efficiency, but may also hurt the interior decor. My suggestion would be to go with a split air conditioner, as they would be efficent, quite, and would maintain the integrity of the restaurant.