I've gotta agree with LG on this...It's always annoyed me the RAF continued to use the .303 for so long - The .50's 750/850 rpm might be slower than the .303's 1,150 rpm, but a .50 is a 710 grain bullet [usually] to the .303's 174 grains, virtually a mini-cannon shell ! And then it's only a 100 fps slower than a .303....that's 'rocks against pebbles' guys...- I voted Mustang and you'll notice they got rid of .30's in them pretty early in the game...The thing that made the difference between the Mustang and the Spit was the Laminar-flow wing, which they finally implemented on the Supermarine Spiteful, abit late for the War...I believe the Spit was more manoevrable, but remember the Mk.XIV was a very heavy fighter, but very powerful...the Mustang always had the greatest range, and agility against the German aircraft, the Fw 190 had the greatest rate of roll, the Mustang was supreme in the ETO in the finish, as the P-38 was in the PTO, but I still love the Spitfire in all it's variants, it 'took the weight' in most of the combat, at least the ETO and MTO, where it's range allowed...