Depending the wet bulb temperature in your area, probably you can't cold the water until 18°c. You have to use a chiller. But chiller is more expensive than cooling tower.
You can use a combined system cooling tower + chiller. Thus select a smaller chiller
First in a cooling tower you can cold...
if operation costs are the same
you can select the chiller which has relatively lower working pressure
(for long compressor life and lower refrigerant leakage)