I have to ask; does it matter? Both armed forces are guilty of gross excesses;

but the soviets commited[sic] mass killings and mass rape which many would argue is worse.

This is a dangerous line of thought; going into false moral equivalency is a tactic often used by apologists, historical revisionists and neo-nazis. I must stress to you to take any line of argument using this mentality with a grain of salt.

The war crimes of the Soviet Union and Nazi Germany must be evaluated in their own 'universes'; war crimes are war crimes. The presence of one does not reduce nor absolve the other, nor does bodycount - when it comes to mass murder, genocide and industrial slaughter, intent is what matters. However, as a caveat, Russian war-crimes in Germany are a direct result of German brutalization of the Russian heartland.

Russian war-crimes are often addressed side-by-side along German excesses in modern histories. Antony Beevor is a prime example, his works address the criminality of the Wehrmacht as well as the rampant misconduct of the RKKA - to the point where very recently his "The Downfall" was banned from Russia because it deigned to touch upon Russian excesses. At no point in doing this however, does he dare to try and use the presence of Russian war crimes to absolve or mitigate German war-crimes. This is the historical norm.

I can't recommend enough you read Mr. Beevor's book, as well as works by Ian Kershaw's Das Ende.