Thanks to you all for your suggestions. Its a toss up but I have decided to do the less traveled Bucharest to Budapest (not the other way around it would appear). The chance to see some of Transylvania as a warm up to Bucharest is exciting and I still will stay a few days in Budapest. Something else I thought of ....... If you have done this part of the river can you get off the boat and do some cycling as I believe you can on other parts of the river(s) on the way to Amsterdam.
Never been on a river cruise but will probably undertake one of these two next year. Eight and nine days respectively. Keeping in mind I would prefer more natural beauty and less industry, does one cruise stand out above the other. Also is it a good idea to spend about three nights before and after at either end of the trip in port. Any and all suggestions appreciated.