OP, It depends on the ship, the build, intended activities, and your play style.
I agree with a previous post about long range & thermal vent or efficient & oversize. Depending on the ship power supply, and capacitor balances must be made. I prefer beam laser if the ship can handle it, but if it empties the capacitor too quick then need to look at pulse for less damage but more over a longer period of time. You may need to have a combo of lasers for your optimal solution. And making a good combo with non-thermal weapons like multicanons that you can switch to allowing some capacitor recovery time.
General Concept: More laser DPS requires more power (power supply) and makes more heat (drains the capacitor faster) so building a ship requires a balance.
Obviously you want the biggest baddest DPS lasering solution. But if you constantly have your enemy perfectly targeted and you want to fire lasers but you can't because your wep capacitor is empty... that's your sign you gotta change your weapon build.
I'm certainly no combat expert, but I have learned enough to know there is no simple best formula. Trying builds using Coriolis and EDSY is a really good idea. Then you gotta try it in actual test combat scenario. Try something that works good, then switch it around a bit.
Keep in mind that if it is for PvE and you are building an NPC murder boat a reasonably good ship & combo of weapons will destroy your enemies. A mediocre build will work just fine. When engineered your ship will easily outclass the NPCs. As you fine tune it to your own playstyle it will get better. Depending on your ship and playstyle it becomes a matter of how many you can fight and how quickly you can destroy them. Destroying them faster reduces how much damage they might impact on your ship.