We will depart on a saturday in July at about 17.00 in Kiel and have to be in Copenhagen next day at 15.30 to reach the ferry to Oslo. There are two possibilities: by ferry from Puttgarden or the longer way over the Great Belt Bridge. We prefer the ferry but heard about heavy traffic before Puttgarden. When is the best time to go by ferry, saturday evening or late sunday morning? As we travel by camper van it doesn’t mind where we spend the night.
Two years ago we took the ferry Puttgarden - Rodby. At that time there were road constructions, so we got stuck in a 25km traffic jam on a Saturday afternoon. Finally it wasn't too bad and we 'only' had about two hours delay. If I'm correct then the road constructions were to make a double lane (2x2) so perhaps the traffic jams are shorter nowadays, but I can't guarantee it. Saturday always is a busy day in summer northwards (Flensburg and Puttgarden). But you depart on 17.00, so perhaps there aren't so many traffic jams in the evening or night. And you're right that you can spend the night where you want, so I would just take the ferry.