My vote would go to Vagabond. I played WC and the Secret Missions first on the SNES. BUt i didn't really get into until i played WC 3 and 4 on the PSX. After that i went back and got them all for my PC. But I really liked Vagabond. He was a steady reliable wingman, and he just seemed like a good all round guy. To me, if i were Blair, he seems like a guy who could be a good friend. You could sit down and have a drink or play a hand of cards with him. I was kind of surprised the first time i saw the Orestes Comm Station raid where he was killed.
I don't understand why someone considers Spirit good... I've never played Wc2 but in Wc1 she's spineless and she isn't entirely good (she and maniac do always risk to die)
So I think Paladin is the best pilot in Wc1...the others aren't too bad but they don't kill many enemies. Maniac and Spirit, they're useless, you must nearly always send they home (and Maniac don't do that)!
in Wc3 I think Hobbes is the best pilot and he agrees to every order. Flint and Vagabond are good to, Maniac and Flash are sure better pilots but they're not so good cause they never do what you want, I hate Cobra so I don't fly with her!
in Wc4 Maniac is a kill-machine...maybe I was not so good at time I played it, but certain mission he killed more fighter than me! Vagabond and Hawk are good too and so in Catscratch...Primate is the best(according to the "skill" displayed)but I don't like flight with him cause he isn't really part of the game.
WCP's wingmen aren't good...I think Maestro is the worst wingman I ever had and his humor is ridicoulus!Stiletto is nothing but she's really gorgeus!
However...Maniac is sure the best character..is amazing!
Primate was in WC3, he just wasn't someone you could choose as a wingman. You could sometimes come back from missions and find him in escort duty on the Victory. I also think he was with Flash (if you chose to battle Flash and won) when they get jumped by some Kilrathi at some point (vague as hell, but eh its what I remember).