I'll tell you that the KI84 is a better defensive plane and is much better used defending a base than any F4U. The F4U is a much better attack plane. They perform best in the situation that fits their flight characteristics better. I'd roll a Ki84 to defend against a CV and F4Us all day. Most people who roll from CVs in F4Us don't take the time to get alt, and that's its biggest weakness when fighting low alt dog fights. F4Us with higher alts will have a clear advantage. The F4U is a very poor defensive plane agaisnt high attackers. It's all about the style you like to play, as these planes have 2 completely different styles in the MA.
I think playing for rank or score is alright. It will help you become better at the game. That being said, if you are good at the game, and only fly easy mode 190Ds or perk planes to easily run away in, you aren't doing yourself a favor to increase your skills. That was my biggest gripe agaisnt Skyrr. Would have been nice to see what he could do score wise in the MA in a less faster, less BNZ style plane. If a player flies old eny planes that don't have many advantages and still score well, you can say they probably do have a good understanding of the game and aren't busy gaming the score for ego. That's atleast where I'd like to be, given that at times I do score higher. I try not to fly the easiest planes because it's not as much of a challenge for as long as I've played the game. I think score can work well to work on your dive bombing skills, bombing skills, and tank skills, to use the stats to measure your performance. That's another thing I use score for. If I wanted to fly easy mode run planes and score high all the time, it really wouldn't be that fun after a while. The different planes in the game can really add a whole different level of skill and undertsanding to the game play that can improve your performance.