For character pilots I would say Maniac. Sure he didn't listen to orders, but he was great at keeping enemy fighters busy while you carry out the mission objectives yourself, and he could shoot them down pretty quickly.
As for "redshirts", I like Primate--he tends to last longer in a fight than the other WC4 wingmen you can choose.
Except the voice replies, does it really matter which wingman you chose? I mean in terms of skill.
Could you say, there is something Iceman can do but Manian can't? For me, all of them looked like the same. Just maybe, major charachters like Maniac or Vagabond don't die in the missions since they are needed for cinematic scenes later in the game.
"Sexy" french accent. Actually, I won't bash you for that, since it's a matter of personal taste. I always found her accent annoying. I prefer something along the lines of scottish or irish accents (in sexy women). (And I know those accents are entirely different). Or maybe Brittish. A girl with a melodic, atriculate voice and a slight accent (by American standards) will strike me as intelligent, and I find that very sexy. Mmmmmm.
Vagabond, by far. He was the only main wingman who didn't have... issues.
He wasn't a rookie (Catscratch), he wasn't crazy (Maniac), he wasn't a complicated love interest for Blair (Angel), he wasn't a simple love interest for Blair (Flint), he wasn't a traitor (Jazz), he wasn't a traitor (Hobbes), he wasn't a pacifist (Panther), he wasn't gun-happy (Hawk), his hate didn't consume him (Cobra), he wasn't arrogant (Flash), he didn't have piles of emotional baggage (Spirit), he wasn't a cold motherfscker (Iceman), he wasn't an irritant (Maestro), he wasn't all pessimistic (Doomsday), he wasn't raised by the Kilrathi (Downtown), he didn't pick fights (Stingray), he wasn't an inexperienced reservist (Shadow), he didn't tritely talk about opening a bar after the war (Vaquero), he used proper grammar (Excel from WC4, I think it was), he wasn't old (Paladin), he wasn't a faceless name (that one wingman guy in Armada), he wasn't a sick b*stard (Seether, remember flying with him? brrr), he didn't drink too much (Hunter)....
I can't think of any issues surrounding Bossman or Knight. Or redshirts like Primate (who r0x0r3d). So I guess they're cool too. But not as cool as Vagabond.