RE: which country had the best fighter planes of WWII
The MK 108 30 mm has a light weight. It could have carried more guns. The MK 108 30mm was good for shooting bombers not fighters. It used a heavy round with low velocity. It had a trajectory that was not good for a fast maneuvering target. Now the Ta 152H is down to two cannons.
I don't understand what you mean by longer legs. Is it range?
I cannot dispute that the Ta 152H had better maneuverability than the P-51D. What is your source?