After a little bit of preliminary testing of heavy lasers compared to small lasers, I'm not very impressed by the heavies.
The power of lasers is their accuracy - target a reactor and pop it quick. Heavy lasers lose too much of this accuracy. Yeah, they seem to do about 50% more damage per projectile, but that doesn't seem to make up for the loss of accuracy.
I've been letting a couple AI controlled ships go head-to-head, one with a few heavy lasers switched out for some of the small lasers(same surface area worth of lasers on both). Theoretically you would see the heavy laser ship do some nice burst damage once in a while and gain an advantage, but the small laser ship is consistently winning the fights.
I suppose the heavy lasers might be better suited for large ship fights(I was testing two 400t ships), but even large ships do a lot of rotation in a fight which will result in misses.
I feel like heavy lasers could benefit from an indirect buff, maybe some narrow AOE damage.
This is only about an hour of testing though. I haven't tested them in lots of different situations yet.