Funny thing how ship design more than size can have a big impact on how crowded you feel.
We were on the Carnival Glory in December, which is 110,000 gross tons with 3700 passengers, and yet it felt VERY crowded pretty much all the time no matter where we went. Yet we were on the RCCL Allure of the Seas, which is 220,000 gross tons with 5400 passengers and did not feel crowded at all, except during a few occasions.
So even though the Glory is half the size, the layout and design of the ship is very poor resulting in a more crowded experience compared to a ship twice the size because of the many public spaces with good layout and design.
Now, with that said, we never felt crowded on either the Eurodam or the Eclipse, so that was a very good thing on both of these classes of ships.