After having experienced the middle deck room in Uniworld’s Venice Cruise, the next year my husband and I were ready to sail the Danube from Passau to Budapest, but on the lower level.
For the most part, I was happy with the room, food and staff. The excursions could have been better described. Most guides but the one in Passau were quite knowledgeable about their subjects.
The organization of passengers onto busses and back again was streamlined and easy.
When in the lower level, the only way to see outside is to stand. The few times I was lounging, I would have enjoyed seeing out effortlessly. If I had it to do over, I’d stay on the middle deck.
I do not recall durnstein.