Sorry if this has been covered elsewhere. Looked but couldn't find anything.
I read somewhere that duals and dual heavies do the same amount of damage. Raises the question for me...is there any real difference between these two weapons? Do dual heavies have any advantages over duals?
They do the same DPS, which isn't quite the same. DHCs have a shorter firing cycle than DCs, which means they fire fewer projectiles, which means that each individual shot does more damage. DCs fire in longer bursts, which gives your EPS regen less time between shots to recover the power. This is balanced by the fact that Rapid Fire is slightly more effective with DCs (since it is a percentage modifier to the number of bolts/salvo), and the slightly higher per-shot power cost of DHCs.
It's mostly an aesthetic. Some ships have different hardpoints for DHCs / dual beams than for DCs, which can make it slightly more interesting to use a combination of both for visual reasons.