I would say that currently destroyers are Hammerhead> Sunder = Medusa >>>> Enforcer. Enforcers are good in junk fleets because they pack missiles and enough OP for a converted hanger - things which aren't degraded by D mods and can be stacked to great and deadly effect. But they are slow, have terrible shields, and low ballistic firepower, making them outclassed by everything they can catch except for civilian vessels.
AI:
Hammerhead is simple - either it has enough firepower to overwhelm the enemy or not. Which is why it so good for AI.
In AI vs AI with both being decently optimized Enforcer performs quite close to Hammerhead. Though I guess significant part is that "rotate to distribute armor damage" behavior helps Enforcer, but hampers Hammerhead. Another reason is that Hammerhead suffers more from converted hangar Talons (even if both bring them, they are harder to afford for Hammerhead and easier to counter with Enforcer flaks).
Then again, there is something to improve about Enforcer behavior too - it could do better with more aggressive play, just forcing armor trades to the end, without allowing multiple vent cycles.
EDIT: after running a few more fights - I guess Enforcer winning is a rare fluke after all, at least outside of Sabot build.
AI is not capable of piloting Sunder and Medusa well enough to make it worth doing. They are only good when making full use of their ship systems.
Player:
For player-piloting Medusa is better at fighting direct combat cruisers, catching frigates and just being generally elusive. While Hammerhead is much better against carriers.
TL Optics Sunder is good at DE vs DE (trivial vs Enforcer, impossible/stalemate vs anti-soft-flux optimized Medusa) and hunting frigates, but can't do much against any cruisers (not enough soft flux damage output). AP Sunder is just a Hammerhead wannabe, so what's the point?
Enforcer... Anything it can do, player-piloted Hammerhead can do better. Except sabot spam.