Spitfire V is the more maneuverable of the two and also slower than the Mk IX. The Spitfire V also has less firepower than the Spitfire Mk IX with only .303 caliber machine guns and 20mm Hispano cannons. The Spitfire Mk IX is faster, not as maneuverable than the V model (but still pretty darn nimble) and has a better weapons package. You can either load .303 caliber machine guns in addition to the 2x 20mm cannons or load up .50 caliber machine guns instead of the .303s.
In my opinion, out of the two, the Spitfire V is the more enjoyable one to fly.
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