Besides posting on CruiseMates, I am answering you privately because you asked the question regarding Amsterdam vs. Budapest so long ago, and I fear you may have given up on getting an answer at CruiseMates.
Your question is something like asking which is better, chocolate fudge ice cream or butter pecan! It depends on what makes a city (or ice cream!) special for you. Both Amsterdam and Budapest are wonderful! I do think there is more to see in Budapest though. You might consider one extra night in each city, or perhaps one in Amsterdam and two in Budapest.
Regarding Amsterdam: It would be a shame to leave Amsterdam without seeing Ann Frank House, van Gogh Museum, the garden markets, and--yes--the Red Light District at night. Other "must" highlights (such as Rjik Museum, Keukenhof Gardens) are included in Viking's tours.
Regarding Budapest: It would be a shame to leave without doing a guided tour of the Parliament Buildings and the Opera House, and having a Turkish bath at Gellert Hotel. The city tour provided by Viking covers Castle Hill and Heroes Square and other city highlights--but your time at each site is so limited. It would be nice to visit the Castle Hill area for an evening tour and perhaps have dinner there. Another "must" would be an evening boatride along the river through the center of Budapest. What a magnificent sight! If you are starting your river cruise in Amsterdam and ending it in Budapest, you will probably enter the city late at light, making the small-boat cruise unnecessary.
I, too, live in Southern California. Feel free to write to me directly at firstname.lastname@example.org
. I have lots of information I can send you as an attachment to an email, detailing what to see, what to do--and even what to avoid--throughout the whole itinerary!