<<Perhaps we should, when given the choice between Stalin or Hitler some people had to flip a coin.>>
Relatively few people had any reason to expect extermination from Stalin and those that did had little to fear from Hitler. Those targeted by Hitler had little to fear from Stalin.
People targeted for death by Hitler or Stalin knew their intended fate and had no need to flip a coin.
Of those not targeted, the choice was pretty clear in most cases. Very few of them would have had to flip a coin, but some of them (particularly the Ukrainians) made a really bad choice. (Bad for them, I mean.)
One of the most comical misjudgments of the war was made by the OUN, Organization of Ukrainian Nationalists, who sent Hitler a congratulatory letter on his initial Eastern Front victories and offered to work hand-in-hand with him in making a world completely free of Jews. Hitler, of course, put them in their place immediately with a letter informing them that the Third Reich did not enter into partnerships with untermenschen (sub-humans.) Eventually, as Aryan S.S. manpower became severely depleted in the course of their encounters with the Red Army, Hitler began to form S.S. regiments composed of various kinds of untermenschen, including the Ukrainians, who often seemed to find themselves in places from which very few would ever emerge alive, the Battle of Brody being a classic example. In the meantime, the Ukrainian Nationalists had managed to further offend Hitler and finally their leaders all wound up in concentration camps, in less than ideal circumstances. One of them (I forget which, but it hardly matters, each one was worse than the other) was finished off when they wrapped him in sheets soaked in cold water and left him outside one freezing winter night. Proving again the old adage, when you sup with the Devil, use a long spoon.
Most people had pretty clear choices. The Poles were the only ones I know of who might have had to flip a coin. Under the Germans they could expect nothing but slavery and under the Russians, more Russian oppression, from which they had only been freed in WWI. Because of their Catholicism, there was a lot of high-level anti-Communism which was bound to lead to some mass executions of priests, intellectuals, artists and writers if the Communists won, but they were already going through this with the Nazis anyway.
This business of "flipping a coin" is mostly (with a few exceptions) pure bullshit. It's what you hear from Nazi collaborators after the war to cover their Holocaust guilt.
The Poles, to their credit, much as they hated the Jews, nevertheless fought the Nazis for the most part but one of their underground armies also fought the Red Army and the communist partisans as well. Usually, as with the royalist Chetniks in Yugoslavia, or the anti-communist Ukrainian Nationalists, an underground army fighting the Nazi occupation, if it's also an anti-communist army, will wind up fighting only the communists. It's too hard to fight a guerrilla war against both the Nazis and the Red Army and/or communist partisans. As the war ground on, and particularly after Stalingrad, when it became apparent that the Nazis were finished, the real issue for nationalist guerrillas was who would control their post-war world, and their real objective became very clear - - to fight the local communists, and sometimes the Red Army as well, and hope for a right-wing provisional government that could attract the support of the Western Allies.
