IMHO any river cruise line is excellent. Viking is almost certainly the largest, with almost an entire fleet of gorgeous new ships, and dozens of itineraries, all over the world.
Tauck is "world-class" in whatever they do. Vantage emulates them to a great extent.
To me, there are fewer differences between river cruise companies than there are between ocean-going cruise ships.
It probably boils down to a very careful analysis of pricing!
SWR
