Well I will offer my input on this since those 3 planes are my favorites.
The P-38 and f6f will be easy changovers, howerver u will have to change your fighting style since u will no longer be the fastest thing in the sky. Alot can catch u so u must learn how to old energy and your ACms.
Both offer great fuel and ordinance.
However if u are looking for a challenge then go with the corsair, it has many different variations for whatever u are trying to do and sticking with one plane will improve your flying ability as well as your gunnery.
I can destroy targets easily with a corsair or f6f because im use to the 50cals and the crossover convergance. however switching tothe p-38 i find my aim is not so good.
With stall limiter off the corsair can do amazing manuvers, however overdoing it will result in a horrible stall that can sometimes be unrecoverable.
Most people will fly the Corsair a few times, and thing of it as a slow hunk of junk that cant turn or run away. It is one of the slowest accelorators so keeping speed is key. However once u master it, reversals come easy, and u can easily trick, outmanuver most any plane.
The corsair is one of the best turners at HIGH speeds. and at 250 with a notch of flaps it can out turn some spits going the same speed.
If u want to learn to fly the p-38 talk to Mrdr who is a Trainer, corsairs, i would go to Mtnman or saber, AKdogg or some others, there are some great corsair sticks. For the f6f im not really sure i have come across a master in that plane yet, as most aces dont use them very often because they fall in the turn and burn class of planes.