Its all about changing your settings, and also about who your flying against
The Russian planes were good. A bit poor on the weapons front, but once you've mastered that then you have a great plane in your hands. Its about what you feel comfortable in and how you manage it. I can fly the Hurricane rather well (well i could when i used to fly) but struggled with the LA7, does that mean the Hurricane is better?
No.
Just means im used to the Hurricane and i know how to use it.
I do agree about the other things you mention though, such as the P51 being erm... crap to be honest. But we all know this. The only thing its good for is free flight and air shows.