Just don't go changing all your heavy mounts to light mounts on a battleship.
The light weapons while extremely useful on smaller ships that can turn fast will often be useless on slower turning ships as the enemies will outrange them or not stay in the firing arc for long.
Thusly I discovered the true purpose of heavy weapons, when I modded my Abby BS to have no heavy weapon mounts, all light.
At the time, I hated the heavy weapons as I always seemed to do more damage with light weapons.