I have learned that it is sometimes better (i.e., ultimately dish out more damage) to go with a smaller weapon you can fire continuously then a large weapon with a limited ROF due to ammo and/or heat issues.
Up to a certain point, I would think. I would opt for a larger weapon when flying a less maneuverable ship. Get as much damage in while the target is in the killzone and then let the capacitors catch up as I turn my ship around. For a maneuverable ship where you can keep the enemy in your sights, well, get a bigger power distributor or simply stop firing the lasers and let the capacitors catch up.
I've not seen heat to be an issue yet, although I've seen my son's Clipper overheat when he uses the shield cell banks.