For me, it really depends on the situation-
Base-defense: Scramble!
I usually go for a 109G10. This bird will get ya up to alt in a hurry, and give ya enough acceleration and decent handling to handle just about anyone.
Base-offense: Charge!
I will usually take a P47D-25 for an offensive fighter sweep over the base, or the d-30 for jabo work (love them dive flaps!). If there are a lot of Jabo's on the way, I'll usually take a D-25 and climb up and pick my fights carefully, then egress when the second wave hits.
Arena-Fighter Sweep: Basic trouble making over enemy territory

This is where I reach a paradox. The -47D-25 with 3 tanks will get me pretty much anywhere, but for this mission I normally take the Mustang. She climbs better then the Jug, and is more suited to the role. Long legs too

Although there are some times I miss that extra pair of .50's.
Furball: The Dweeb in Me.

I've found that the 109G10 is probably one of the best planes to mix e-fighting with a furball. The ranges are short, so you can stick that MG/151 right into their tail feathers and pull the trigger

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-Rebel
JG2 "Richtofen"
"You Rebel Scum"