My favorite WC1 fighter is the Raptor, definitely. The Rapier has that paper-thin side armor. My personal view is that the Rapier is like a super version of the Hornet (extra speed, weapons, and shielding, with its combat style built around speed and long range fighting), while the Raptor is like a super version of the Scimitar (with a combat style based around giving and taking a strong punch). I do not understand the guys who prefer the Scimitar, though, because the Raptor is superior at everything--more shields, more speed, more missiles, and optional neutron guns (you can switch to mass drivers only if you want that). Maybe they just like to give themselves a bigger challenge.
My favorite for WC2 would have to be Broadsword. That thing is the closest to indestructable of any ship in any WC game! With its back AND side turrets, it can attack enemy fighters from any direction. The only problem is that Drakhri fighters tend to stay just out of range of the turrets and mass drivers, and shoot at you with their long-range lasers.
My least favorite WC2 fighter would have to be the Epee. Sure it has great offensive power, but its shielding is significantly poorer than the Super Ferret (the Ferret with HS missiles), and it is slightly slower. I prefer the Ferret over the Epee any day.
For Privateer, I would say that anything except the Tarsus is good. The Centurion has the lightest shields, but it is built for speed and has four guns. The Galaxy has medium everything, plus top AND bottom turrets (too bad they don't auto-fire like WC2 turrets do). The Orion has the heaviest shields and armor, but has a bit less offensive power since it can only carry a single missile launcher.
My favorite in WC3 would have to be the Arrow--unparalleled speed and agility, plus the Shelton Slide! I just wish it could carry all the types of missiles--it would be great to have Leeches to use against Pahktahns. At the other end, I hate the WC3 Longbow--it is a pig to fly, and you can forget about using your guns against Darket or Strahka fighters (The WC4 Longbow is a bit of an improvement though).
In WC4 I like the Bearcat--it is faster and more agile than anything in the game, and has great attack and defense power (although the wide-spaced guns mean that you may have better aim by shutting off the auto-tracking and aiming manually). I dislike the Banshee because its four laser cannons can't damage anything, and I can't aim worth a damn without the ITTS, so the Scattergun is out.
My favorite WCP fighter would have to be the Panther. It has good speed, agility, and weapons without being hyper-powered like the Vampire. The Pihrana, on the other hand, has lots of armor but practically NO attack power--its 2 ion / 1 laser cannons and 4 HS / 2 IR missiles are weaker even than the Arrow, which is the 20+ year old fighter that it was designed to REPLACE! Good thing you only have to use it in the first two missions of WCP--killing that Manta in the second mission is near impossible unless you either have most of your missiles or some Stormfire rounds left, or if you can get it in a crossfire between yourself and your wingmen.