Given that the P51D had the same Merlin engine as the Spitfire why was it actually considered a better fighter? How was it that it could travel further than the Spitfire?
“Better” is a subjective term. The P-51 could fly all the way to Berlin, tangle with the best fighters the Luftwaffe had to offer, and then fly home. That made it a better high-altitude, long-range escort than the Spitfire. However, at the beginning of its flight with a full fuselage tank, the P-51’s center of gravity was off and trying to fight at all would send it into a spin.
The Spitfire’s design didn’t leave a lot of room for fuel, primarily due to it’s thinner wing, which didn’t have room for fuel (unless the weapons were removed, as was the case for photo reconnaissance versions).
That being said, the mk IV spit was at least as good- if not better than – the Mustang in a dog fight. It just didn’t have the legs to go deep into Nazi territory.
So the Mustang was the better long-range escort, and the Spitfire was the better short-range interceptor. They were both excellent planes when used in their respective roles.