My husband commuted by train from Cologne to Essen for a month, but it didn’t really work well. When you look up the connection, it says 53 minutes from Mühlheim station to Essen HBF, but the train never kept to that schedule. Sometimes it took two hours because he had to change trains in Duisburg, or ICE trains always had to be given priority. By car, it takes him 45-50 minutes, which is much less exhausting for him. He says the 70 km are much more relaxed for him than before in Cologne with the KVB for 35 minutes (he also worked in Cologne before).
That’s why we are looking for something in the middle. I will commute by train to Cologne later, but the travel time should be reasonable. At the moment, it takes me 40 minutes to get to work from the east of Cologne to the city center, which is okay. Under an hour would be nice :)