@BIG-BENNIS-MAGIC
I don't think the firing cycle has much to do with it because we are talking about 85 damage shots for uef, vs ~2000 hp frigates, so the percentage overkill is tiny compared to say t3 tanks. uef could theoretically even gain from a slower firing cycle because the higher alpha damage could help knock out enemy units faster, just like percies vs bricks. I do think the firing cycle gives cybran an advantage in killing enemy engineers around naval factories, though.
Edit: It's also not totally clear whether a slower firing cycle leads to less or more "overkill." In many land battles, the uef gun acu will have less overkill when facing t1 arty (except uef arty) because the slower firing cycle means it won't fire a waste shot at a unit that was already about to die from the previous shot, while an aeon gun acu will often shoot 3 times at 200 hp units that would have died from just 2 attacks, but it didnt' retarget since the 2nd projectile hadn't hit yet. So the projectile speed and distance matters too.