I posit that the Pirate Frigate is not fun to sail in its current iteration; this is largely due to the terrible upwind power of the ship.
This problem came about when the devs changed the sail profiles for all ships to match their actual deployed sails (a good change overall). Unfortunately for the Frigate and Pirate Frigate, they seem to be missing a Main Topgallant Staysail which every other ship in the game has deployed. I suspect the pirates sold it for more rum...
If you examine the speed of the Pirate Frig before the patch here: https://sites.google.com/view/speedtrials/old-sp