I have been on two river cruises in Europe with two different companies and can't help but compare. While we enjoyed our cruise with Viking, I felt Uniworld was a better experience.
First, as others have noted, docking in Le Pecq instead of Paris is very inconvenient. Their smaller ships can dock in Paris, so why not ditch the longship and dock in Paris? The shuttle Viking provides to/from Paris were often at inconvenient times, and not frequent enough. On the last day, we went into Paris on the shuttle at 9 am, and returned via taxi at about 3, and it cost us 50 euros and took 50 minutes. If you went back during rush hour, it would cost a lot more since in Paris the meter runs when you're stuck in traffic.
They don't provide enough information in advance of the cruise about the shuttle and the fact that there is a briefing at 6:15 pm followed by dinner at 7 pm on the first day. I had to write to the ship's concierge to find out how late we could get to the ship from Paris, where we were spending the day, and to find out that the Viking shuttles would leave Paris at 5 and 9 pm on boarding day. Too late in our opinion, so we arranged for a van to take the four of us and our bags to the ship, which cost us 90 euros.
Decor: I find the Scandinavian wood-laden decor a bit stark and blah. Uniworld's ships are more opulent, and each cabin is decorated differently. While the Uniworld ship I was on was a bit over-the-top in the decor category in my opinion, it still gave a more luxurious feel.
Crew: Both crews were very nice, friendly, and efficient. But there was a certain something about Uniworld's crew that beats Viking. They have a butler in a tuxedo who greets you for dinner every night. They introduce the dining room crew and chefs on the first night in a humorous and fun "show." The captain made himself visible at dinners on Uniworld, whereas the captain on Viking was invisible except for briefly on the last night. I felt more taken care of on Uniworld, for instance water glasses were always kept full. But to be fair, we had some great waiters on Viking and made a point of sitting in their section every time. The Viking cleaning crew did a great job and always greeted us in the hallway, but on Uniworld they greeted us with our names. Small things like that add up.
Dining: The food on Uniworld is gourmet all the way -- I never had anything that wasn't OUTSTANDING. On Viking, I would say the food is good, but usually nothing to write home about. On the Uniworld cruise, the chefs -- they have their own pastry chef too -- were French and really spectacular. There is one more course on Uniworld too -- salad/soup. Many times on Uniworld at lunch the pastry chef created something special, like homemade ice cream, and served it herself.
Itinerary: One good thing about the Viking itinerary is that they give you an extra day in Paris at the end. Previously, they spent the last day in Conflans. Hmmm, Conflans versus Paris -- Paris wins, hands down! I think they made this change to help make up for the docking in Le Pecq situation. They also gave a night tour of Paris, which helped make up for it too. At the D-Day beaches stop, Viking gave us each a rose to leave on a grave of our choice, and they organized a really nice ceremony at the American cemetery. We sang the National Anthem, had a moment of silence, and a French woman from the cemetery said a few words of thanks to the American people. They called up the veterans on the cruise to the front and said a few words of thanks to them. It was all very moving. The Giverny stop is a must-see, and I highly recommend going after April 1 when it's open.
Overall, we had a good time on the Viking Rinda. Good, not great.
The cabin is miniscule, but we expected that since it's the cheapest. The beds are a bit small, but comfortable. We thought the pillows were too soft. There are lots of 110 electrical outlets. The sliding door to the bathroom didn't give a lot of privacy, and it wouldn't stay shut when the ship was moving (there was no latch). The cabin makes efficient use of space, for instance our suitcases bit under the bed.