At the risk of stating the obvious, all cruise ships are the same when you get out at a port.
So any differences have to be while you're on board - let's say 16 hours. Of that, about half is spent asleep, leaving 8 hours.
So eating, drinking and (weather permitting) outdoor enjoyment account for much of that time.
Secondly, despite what is written on this subject, cruise ships are far more remarkable for their similarities than their differences. The big differences are not found on board - they are the ports of call that an itinerary visits. The Caribbean is very different to the Baltic, for example.
Lastly, there is one big variable that neither you nor the cruise line has control over: fellow passengers.
Luckily, cruise lines offer so many alternative things to do (including doing nothing!) that if you don't care for something, move on to the next thing. In a word, choice. Virtually limitless choices.