This is meant to be a halfway tongue-in-cheek post, so remember that when replying to it.
The Spit 16 has a reputation, along with the Lgay, for being a "dweeb" plane. That is, inexperienced pilots use it as a crutch to stay competitive. Can't say I blame them, but there it is.
That said, the Spit 8 is just about as good, but nobody goes around denigrating the Spit 8 driver's choice of ride, except inasmuch as some people call any Spitfire a dweeb plane.
Also, at 10 ENY instead of 5, you get twice as many perk points per kill in a Spit 8 as you get in a Spit 16. Since they're pretty close to each other in combat effectiveness, that's a pretty good deal.
When I fly a Spitfire, I generally fly a Spit 8. I keep my convergence very short, as in 275-300 yards, and at that range the 4x.303 machine guns do OK. Not great, but OK, and if you're careful to fire short bursts with your cannon and conserve your ammo, there's no reason a Spit 8 can't kill almost any fighter with a 1/2 second burst from 200-400 out.