Energy weapons I may put in small mount: Ion Cannon, Burst PD Laser, AMB. Ion Cannon is EMP damage. Burst PD Laser does not need IPDAI to track reliably and has enough stopping power to stop a missile or two quickly enough. AMB is for Afflictor, who recently had two universals downgraded to hybrid.
In Medium Mount: Ion Pulser/Beam for EMP or Heavy Blaster for DPS. Heavy Blaster for ships with only a single mount for assault, like Heron (which has a universal, but same idea). Next release, with Pulse Laser getting better efficiency, I may consider that instead of Heavy Blaster. Currently, Pulse Laser is not efficient enough.
In Heavy Mount: HIL, Tachyon Lance, or Plasma Cannon. Plasma cannon has the highest DPS, passes though missiles and fighters, efficiency is not too bad for a heavy weapon, accuracy is better than heavy ballistics not named Gauss, and good enough against armor. I would consider beams for anti-armor if the ship has plenty of kinetics in other mounts. Also, targets with high hard flux cannot fully block tachyon lance strikes with a shield.
In practice, small and mediums are usually filled with a ballistic weapon, often kinetic, with Afflictor being the obvious exception (AMBs). Large mounts, at least on Prometheus II, I used Tachyon Lances to compliment the kinetics. In previous pre-0.8 releases with stronger skills, I used Heavy Blaster on Heron and Mule with universal mount, but I doubt that works well today.