Kuvult, as much as it makes sense to measure reshayim against each other (is there a gemora measuring Haman v Pharaoh? We compare Lavan w/ Pharaoh in Hagaddah, but somewhat rhetorically), Soviets were worse for multiple reasons.
First, way more victims of Communism – more than 100 mln if you count Chinese communists, see “Black books of communism” for details per country.
Second, they came earlier and made mass murder a reality (WW1 had a lot of people killed, but at least laws of war were mostly followed). They killed and exiled millions, including Yidden, while Germans were still having rock-n-roll in the 20s. Nazis came to power in response to Commies and were able to get more power in divided Europe.
Third, as you are saying, their effect on all people, including Jews, was way more profound. With all Nazi unimaginable cruelty, the horror lasted for several years. Those who were lucky to survive recall those years or even months (like Hungarian Jews) for years. Soviets affected Russian & Ukrainian Jews for 70 years and Litvishe and Latvian for 40. When you see Rusim in Israel or on Brighton Beach, these are people whose grandparents did not get Jewish education …