It really depends on what you are doing with it. For the AH MA with it's focus on low altitude combat you want to take the Spitfire Mk VIII or Spitfire Mk XVI. Both have lower altitude tuned engines than the Mk IX or Mk XIV and will be a bit better at AH altitudes for it.
Between the two the Spit VIII has full span wings so it'll turn a bit better and it carries a bit more fuel so it'll fly further.
However the MK XVI is a bit faster, climbs a bit better, rolls significantly better, and has two .50 cals backing up the Hispanos instead of four .303s as on the Mk VIII.
The MK IX is an earlier stopgap fighter that has it's best performance altitude at 25,000ft, well above most AH fights. It is armed and winged the same as the Mk VIII, but is slower and has a significantly lower climb rate, and therefore acceleration. It is lighter than the Mk VIII so it will probably turn slightly better, though with a weaker engine it is hard to say.
The Mk Vb is an early Mk V armed with Hispano Mk Is which are drum fed and so have only 60 rounds per gun. It is much less potent than the Spit Vc at +16lbs boost that we used to have. It'll turn better than the later Spits, but other than that is it heavily outclassed. Only reason to use it in the MA is if the others have been disabled by the ENY limiter. It is a much better scenario plane than the old Mk Vc was.
The Spit Ia has had it's boost raised from +9lbs to +12lbs so it performs better than it used to, but in the MA it is still only good for having a bit of fun in or humiliating your opponent. It is a great scenario plane though.
The Seafire is, well, a Seafire. It takes off of carriers. The MK V out performs it, but it does have 120 rounds per cannon.