We chose Avalon because we preferred the cabin layout over other vendors. Price and tour itinerary and availability were also factors.
There was some confusion in not being met at the airport and we had to call Avalon and wait around for a while but eventually we got picked up. It was wonderful to suddenly be in Paris on two summer's days. We did both the bus tour of Paris and Versailles on day two and enjoyed them. The guides were excellent. Note that the bus tour points out the museums but does not stop at any of them. You need to arrange museum visits in your spare time. On the third morning we independently took the Metro down to L'Orangerie art museum and got back to the hotel in time to get the bus to the train station. The hotel was excellent, the location delightful (near the Arc D'Triumph). Part of the charm of Paris was buying bread, cheese and yogurt in the close-by market and eating lunch in the lovely park nearby.
The transfer to the train to Luxemburg and then the bus to the ship went smoothly and was well organized and supervised. We found the ship very nice and loved the view from our stateroom. The five days we spent cruising down the Moselle were blissful. My favorite part was sitting on the sun deck and watching the vineyards, bridges, castles and other traffic go by. The Moselle during this stretch was pristine, no industry, just endless vineyards and small towns. Each day we stopped and toured one town. It was very enjoyable and almost magical. The city of Trier has amazing Roman buildings including the extant throne room of Emperor Constantine. I loved that.
The cabin was very nice with a huge 11 foot (?) full length window on the outside. The cabin is not large, the king size bed takes up most of the room. But it was comfortable. We could of used a few more drawers in which to store clothes, etc. The bed was very comfortable and the bathroom nice also. The view from the window was one of the treats of the voyage, although we had to draw the curtains at times when docked as we often woke up to swans or dog-walkers about 5 feet from us looking in!
The staff did a good job of taking care of us.