Which I still need to try is Laser turrets. I have x-ray turrets and 600k BFCs. I wasn't aware I should turn them on for ADF so gausses did the work. I wonder what their performances will be.
Regarding lasers, you should use them in ADF only if they have enough range to shoot at least twice before the enemy missiles hit you. To make an example, if your laser 10cm turrets have 210k km range, but the enemy missiles have a speed of 30k kms, final defensive fire is still the best solution as you cannot be sure you'll shoot at them twice, and final defensive fire by its own nature has much higher chance to hit because it targets the enemy missiles at 10k km.
Regarding gauss vs lasers, as soon as you research a couple of gauss tech levels gauss are strictly better than laser in a anti-missile situation. And the more you research gauss, the wider the gap becomes. But gauss are a strictly anti-missile weapon, while lasers are not.
A 10cm laser turret can be used with profit against enemy fighters and even against enemy capital ships if they are in range, while gauss will be limited to anti-missile situations barring rare occasions. As such, the question then becomes what your fleet is supposed to do. If you are using a missile fleet, are confident you can keep the enemy at range and you know the enemy is not heavy on fighters or FACs, then you don't really need laser turrets and gauss turrets are better against missiles.
If you are instead using a beam fleet or your enemy uses beam fleets and/or you are not confident you can keep at range and/or the enemy uses a lot of fighters/Facs, laser turrets can be a good idea as they can be used in multiple situations. They are basically the most versatile thing you can have... You can also opt for a mix of gauss and lasers in this situation.