Just as a point of comparison, I compared Nautica and Voyager.
Voyager is 46K tons, 700 pax, 447 crew (ratio guest to staff: 1.56)
Nautica is 30K, 684 pax, 400 crew (ratio guest to staff: 1.71)
People have reported that the Oceania ships feel a bit more crowded than similar Regent ships, and you can see why--that extra tonnage translates into more public space and bigger cabins.
