For STO purposes it does not matter whether you go single, twin, triple or quad turrets. Even for ships it is no longer a very important decision since Steve changed the way PD weapons fire at missiles. It used to be that quad turrets were the best for taking down big salvoes whereas single turrets were the best for making sure all salvoes in a single increment were stopped, with twin and triple a compromise between them if you could not afford to research and build multiple types of turrets for your PD ships.