Some pirate ships are cheaper and inferior versions compared to standard (Wolf, phase ships)
Some pirate ships are identical to standard aside from paint job (Vanguard, Enforcer, maybe others)
Some pirate ships are significantly or heavily modified from standard, ranging from different system (Eradicator) to overhaul (Falcon, Atlas)
When d-mods were added to the game, pirates were supposed to be fodder who used inferior junk. In later releases, pirates shifted from cheap junkers to evil hackers or artificers that churn out crazy modifications to whatever they use. Every new P ship we get in recent releases is either a reskin or heavily modified version of the ship, no more cheap inferior versions of ships like Sunder with no large mount or original Falcon (aside from rusty skin) that did not have small turrets ahead of the mediums.