Eastern Europe is definitely cool, 'cuz you not only take out an ARM, you also prevent 3 ARM (in Germany and South Europe) from attacking Karelia T1. Watch out for his forces in Norway & Ukraine though–heavily reinforce Karelia. Eastern Europe has a tendency to majorly backfire if you don’t properly reinforce Karelia & Russia, or you use too many forces in the initial attack.
Personally, however, I prefer a more modest attack on Finland/Norway, while sinking the TR in the Baltic (at least) and moving the fleet to UK waters. Finland/ Norway is difficult-to-impossible for Germany to get back, provides a ready landing point for Allied seaborne forces, and best of all, whatever ARM you have after the attack is “safe” from German counterrattack–unlike in the Ukraine and East Europe. As USSR, I never waste ARM.
Just my $0.02.
Ozone27