Well, if I ever get to play these series:
I somehow love Russian planes over any other planes, but anyway as for Early eastern front: Mig-3, I-16 and Yak-1 although I'm a big fan of the La-5 series which entered the scene only in 1942, a total beast (as modeled in 1946, that is). Oh, and my fav of all time, the american P-39 of course...
(and I do prefer it with a red star)