YEager has made some other bad statements about the P-38 but the fact of the matter is that the P-38 dominated the Pacific and Mediterranean.
Over Northern Europe it didn't have such a good reputation and I've never really read an authoritative reason why. My general assumption is that a combination of being a relatively complicated aircraft to master, the extremely cold air of Northern Europe disagreeing with the P-38's engines, British AviationGas issues, and a complex logistics system caused the P-38 to fall from favor once the bugs had been worked out of the much simpler Mustang which by virtue of being powered by a British engine had no trouble with British AVGas.
The Mustang was probably the best allied fighter of the war for average pilots.
The British got the first batch, and needed planes, so they didn't wait for the superchargers. Probably had a lot to do with it. Then there was a problem with the flaps that need modifications.
That's not to mention bailing out. The pilot had to crawl out on a wing, over an engine, before dropping, to avoid being hit by stabilizer.