Cooldown is a a very important factor in planing your strategy and designing your ships in GO2. Even though you can lower the cooldown time of your weapons (advanced science research) the simple difference in cooldown rounds for every type of weapon is something that needs to be considered while designing your ships and deploying your fleets into battle.
Ballistic Weapons: 1 round
Laser / Directional Weapons: 2 rounds
Missile Weapons: 3 rounds
Ship Based Weapons: 4 rounds
The only way to lower cooldowns are commander abilities and certain researches