I agree that ammo isn't a very important consideration.
I think your point on DPS/OP is wrong because it does not consider the types of ships that mount energy weapons. They tend to be more mobile than their ballistic counterparts - capable of hit and run tactics where alpha strikes, overwhelming an enemy, and raw damage output are most important. These are ships that can control the pace and range of engagement. Yes longer range weapons will shoot them a bit on the approach (maybe!), but in general they can get in, overwhelm, and get out to vent. IMO the only real failure in this role is the Aurora, though with the missile tweaks it may re-emerge as the premier missile ship (if only large mount missiles were better!). Of course if an Aurora with 3 Heavy Blasters actually catches something, it tears them to shreds...
Ok, I was obviously setting myself up for a fall by making a sweeping statement regarding *all* energy weapons being bad; this is of course false, everything has a niche.
There do exist energy weapons that fulfill the alpha strike niche (AM Blaster, Mining Blaster, Heavy Blaster, Plasma Cannon), where no comparable ballistic weapons exist.
However:
1) Missiles fill the alpha strike roll *so much better* than Energy weapons; they do more damage, and free up more of your flux for shielding yourself during your hit&run maneuver.
2) What about all the mid-line energy weapons that compete directly with their ballistic counterparts? Pulse Laser, IR Pulse Laser, Autopulse, Mjolnir? They're all terrible by comparison.
3) What about PD? Energy based PD options are all* laughably bad compared to flak & vulcans.
*Burst PD used to be passably good before it was inexplicably nerfed a few versions ago (and oddly, vulcans buffed to the god-tier weapon we have today)
Anyhow, this is going way off topic. That's enough from me.