Both of which are capable of destroying turret-only defenses with minimal effort, just by staying out of firing range. 3-6 Fighter Squadrons alone will be enough to keep them at bay, which is why I never really understood why people spam Hanger Defenses - too many is really a waste of tactical slots.
What about the Vasari? With their Phase Stabilizer network and Antorak Marauder Phase Nodes, they can send a fleet to defend any part of their empire at anytime from anywhere. So instead of needing to put up short-ranged turrets that may or may not aid in a fleet battle, they can fill the remaining Tactical Slots with Regeneration Bays and Hangar Defenses. As it is, the Vasari have the strongest fighters around.
And, if they're already engaged in something so critical that they cannot send anything at all, it's not as if a turret-based system will stop the attacker with 10 tactical slots gone in the redundant Phase Stabilizer.