Kruse's 1991 article "Mechanical System Strategies for Energy Efficiency" discusses chiller motor choices.
One major decision to make when selecting a chiller is the type of motor it uses. Some use hermetically sealed motors which are cooled by the Freon in the chiller. Others use open drives which means that they are cooled by the air in the room. Open drive chillers use less energy since they don't have to cool the motors. The savings is usually at least 10% but can be as much as 25% depending upon make and model. However, the motor must be cooled somehow. In most climates and circumstances, the chiller room can be inexpensively ventilated so as to remove the heat from the motors. In cold climates, the motor heat will offset the need to heat the room thus offering additional savings. In warmer climates more of the savings are traded for the cost of cooling the room, but the savings are still worth investigating.