The Manta beat the Patrol Ship 9 times out of 20 battles - the Patrol Ship beat the Manta 6 time out of 20 battles, and there were 5 cases of total annihilation. Manta > Patrol Ship. The exception appears to be under the cover of their respective cruisers, in which case the Patrol Ship always seems to fair better (the fighters go after the opposing cruiser: the Patrol Ship does damage and lives, the Mantas usually get caught in cruiser-cruiser crossfire and fall without the Confederate Cruiser even targetting them.)
The Hawk beat the Manta 10 times out of 20 battles - the Manta beat the Hawk 3 times out of 20 battles, and there were 7 cases of total annihilation. Hawk > Manta.
The Confederate Gunboat has not been tested by me, but would typically beat any of the other three by means of its heavy rockets - although its shields, manouevrability and primary armanent are absolutely laughable, the heavy rockets are dangerous. Should the rockets miss, the battle will most definately side with the other ship. In swarms, the opposing starfighter would stand a better chance against the Confederate Gunboats.
Therefore, the Confederate Gunboat is typically the most dangerous of the four spacecraft. In swarms, however, the Hawk would most likely be pre-eminent.
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-Lyat Esponer Corsair