I tend to pick a plane based on the mission. For example if there's a bunch of high "pickn" ponies (and there usually are) I'll up a d9 or an la7 (cause I can't hit much with k4) and for base defense I'll up a la5 or a spit (depending on eny) If I'm running an attack mission I'll usually take an F8 unless there's lottsa enemy which in that case I might take a pony or a jug.
I think this is something a lot of players overlook. It's okay to only fly one plane and learn it's strengths and weaknesses, however, flying a p47M or P51 ect in base defense against a bunch of CV planes will lead most to disaster. Not saying it can't be done, but it will be challenging if you dont roll from a back field or take the time to get alt if you can.
Some planes are suited much better for base defense like spits, La5/7s, Niks, and Ki84s, and some for long range attack (generally most American airforce planes) and a few German planes like the 190s, or Ta152. Some are built for good mid air combat like the 109s, Spits, F4U, Fm2, a6m, C205, and Yaks, varying between low, mid, high alt fighting. Some of the long range attack planes are good for mid air combat as well, and some of the defense planes are too. Long range planes generally aren't good at base defense, and low mid air combat planes generally aren't good at long range attack.
A lot of this game is about flying the right plane for the right situation. This can make only flying one plane very difficult in certain situations, and you may even log of that situations isn't what you want. That's when mixing up your plane choices for the situation is very helpful and can be beneficial in getting more kills and being more successful.
