Love ‘em both, but in different ways.
Re: size, remember that VO ship capacity is only 930, which is not so many for a “full size” ship. We’ve never felt crowded, and as others have said, it’s very easy to strike up a conversation if you’re so inclined.
We actually enjoy the opportunity to seek out a quiet corner in the Living Room on VO to read, etc. Sometimes the VR experience is a bit too intense for us, as there is nowhere to hide and at times we feel we’re in a fishbowl.
It seems nearly all VR pax are well-travelled. As Viking tries to fill more and more ocean ships, at times the experience is diluted by some less-considerate passengers.
Both are great in their own right and we purposely mix our river and ocean trips to experience the unique features each has to offer.