Here's my take on the WC3 craft:
Arrow:
Light and fast, but with decent shields unlike the Epee and Ferret--you can actually take on a wing of bombers in an Arrow. With its eight missiles and Laser/Ion guns, it is like a slightly lighter, faster version of the WC2 Rapier.
Drawback: You can only carry HS/IR missiles. I would really love to be able to carry Dumbfires to knock out a Pahktan or Vaktoth in one shot.
Hellcat:
Despite carrying only six missiles to the Arrow's eight, it is able to carry all types of missile. Also, it has slightly greater shields, armor, and gunpower, but less speed.
Drawback: The Hellcat only does 120 damage per shot compared to the Arrow's 96 damage per shot, and that's only if you are firing from within the Neutron guns' much shorter range. The result is that the need for close-in combat with the shorter windows to "take a shot" reduces the advantages of having the heavier guns. The WC4 version of the Hellcat with longer range Particle guns instead of the Neutron guns fixes this problem (it also gets 148 damage per shot). I think that if the WC3 version also had Ion/Particle instead of Ion/Neutron, then it would go a long way toward making it seem more equal to the other fighters.
Thunderbolt:
Carrying the heaviest guns of any fighter before the Excalibur becomes available, enemy fighters simply disintegrate before it . . . IF you can hit them, that is--its slower turning rate makes it difficult to track Darket and Strakha light fighters. However, against heavier targets it reigns supreme, and its single torpedo makes it preferable to the Longbow for any mission where you don't need more than one torp.
Drawback: The Tbolt's armor is a bit on the thin side for such a slow fighter.
Longbow:
With four torpedoes and SIXTEEN missiles, the Longbow can blast apart anything that it can hit. Unfortunately, its slow turning rate makes it nearly impossible to track Darket or Strakha fighters. Ideally you should be able to take them out using missiles, but in practice you may run out of missiles before you run out of targets, leaving you in trouble. In general, it is better to take the Tbolt and get the better guns, speed, and maneuverability unless your mission calls for having more missiles or torpedoes than the Tbolt can carry.
Drawback: Short range Neutron guns--see Hellcat, above. I suggest using the WC4 Ion/Plasma combination instead.
Excalibur:
With twelve missiles and an unmatched set of guns, and with more speed and agility than the Hellcat, the Excalibur has enough attack power to make it a juggernaut. Unfortunately, its defense power does not match.
Drawback: Excalibur's armor is equal to the Hellcat's, which would be okay except that Excalibur missions tend to have you up against much larger waves of fighters than non-Excalibur missions. Armor of 150 instead of 110 would be more appropriate.