Did you know that you get one capitol ship free?
I was lead to believe that was common knowledge?
Of the five types of ships Pirates will throw at you, the Cutthroats and Rogues will chase trade ships blindly, Corsairs will go after your tactical structures, Reapers will chase your strikecraft (or follow the Corsairs if they don't find any), and the Pillagers blindly rush to bomb your planet like any other siege frig.
Rogues are essentially light frigates, Corsairs are HCs, Reapers are flak, and Pillagers are siege. Cutthroats seem to get ripped to pieces by fighters, so I presume they have the same armor type as LRF.