Issue isn't F4F v Spitfire. The Spitfire was the most preferred plane by the British, but if there had been enough of them, they wouldn't have operated any of the other types of early-mid war as air-air fighters (like Hurricane, P-36 and P-40 variants, Buffalo, even Fulmar and Gladiator occasionally operated from land bases, etc). The issue would be F4F v those other types, assuming there were F4F's to spare. The F4F had a consistently far superior fighter combat record to the Hurricane in the Far East, not just in a few fluke combats but Hurricanes had a highly disadvantageous kill ratio v Japanese Army fighters all the way through 1943. The F4F didn't have as superior a record to the P-40, but still tended to get better results v the same Japanese fighter opposition. So it's not at all obvious the F4F wouldn't be a credible or even superior substitute to the Hurricane or Tomahawk in Med theater situations, especially the Hurricane. From Malta for example remember that the Hurricane's kill ratio result v Bf109E was 0:35. It accomplished other things of course, shooting down Axis bombers and it did much better v Italian fighters, but so could the F4F have done those other things, and how much worse could it possibly have done v the Bf109E? The record of Hurr and P-40 generally v 109 wasn't as lopsided, Malta 1941 was the poorest showing of the Hurricane Bf 109E, but still Hurr/P-40 v 109 tended to be clearly in favor of the Bf109 in most cases. So we shouldn't imagine that the Hurricane and P-40 were completely competitive with the Bf109, and that the F4F might somehow give up that parity. It's very plausible that the F4F would have done no worse than Hurricane and P-40 v German fighters in Med theater situations, just as it better than those two v Japanese fighters, again especially better than the Hurricane.
Of course, even the Spitfire had a (much) poorer record v the Zero than the F4F, but it had certain clear advantages in performance that can't be ingored. I wouldn't suggest generally substituting F4F's for Spitfires, not in most cases anyway. But compared to the 'second rate' types used by the British, the F4F was at no particular disadvantage as a practical air combat fighter IMO, and it showed that when the types operated alongside. Consider also that the P-36, ie French H-75's did better than the Hurricane v Bf109's over France in 1940, and that was a fairly similar plane to the F4F, inferior overall if anything.
Joe
Of course, even the Spitfire had a (much) poorer record v the Zero than the F4F, but it had certain clear advantages in performance that can't be ingored. I wouldn't suggest generally substituting F4F's for Spitfires, not in most cases anyway. But compared to the 'second rate' types used by the British, the F4F was at no particular disadvantage as a practical air combat fighter IMO, and it showed that when the types operated alongside. Consider also that the P-36, ie French H-75's did better than the Hurricane v Bf109's over France in 1940, and that was a fairly similar plane to the F4F, inferior overall if anything.
Joe