The option of the Prague add-on to the Danube cruise made it perfect for us. The whole cruise was outstanding, apart from maybe too much shore walking; I have a trapped nerve in my back (awaiting surgery) and arthritis in one knee, hence I had to limit my on-shore endeavours.
The cuisine was excellent. We ate normally in the lounge - breakfast and lunch - and found the array of food there just perfect. The soups were particularly notable.
To end in Budapest was just perfect. The evening cruise up and down the Danube was even better than I had expected and I had done it before, albeit 16 years ago! To start with Prague and end with Budapest was ideal from any perspective. While Vienna is undoubtedly a lovely city, we live in London and the similarities are there, whereas that doesn't apply to Prague or Budapest. The daytime cruising was excellent e.g. the Wacchau Valley, as were the stops at small towns such as Durnstein. Overall, an enriching experience.
Maximum benefit made of a small space. Our cabin stewart Mirko was outstanding.