Steven Den Beste treads where 100,000 aeropundits have gone before
Ultimately, they switched to the Mustang, which was the prestige fighter of the European theater; beautiful, fast, deadly and long ranged: it was the best fighter the Allies had in Europe, and for bomber escort they needed every bit of it, especially after the Germans began to fly the Me-262.
Best fighter is truly meaningless unless it is stated what specific role it was best for. The P-51 Mustang was without doubt the most effective long range piston engined daylight escort fighter of World War II. Of the mid-to-late war piston engined fighters, it was not the best defensive fighter (Fw.190-D or Spitfire 19) or nightfighter (He.219 or Mosquito, various) or day/night intruder (perhaps Mosquito FBVI) or multi-role fighter (no clear winner).
Comparing fighters with different roles is pointless and thus there was no single ‘best fighter’, just ‘best fighter in some role’. The P-51 had good all round performance, very good cockpit visibility and most importantly had the range to carry out the strategic escort mission that other even higher performance piston engined fighters did not have. But as all combat aerocraft do, it also had its weak points and like all USAAF fighters of the time was certainly under-armed by 1943-1945 standards and had GC issues at some weights. How about “The P-51 Mustang was the most important USAAF daylight fighter of the European Theatre in mid-to-late World War II period”. A much safer contention.