I haven't been on Royal, we have primarily been on Carnival, with one each on Princess and NCL.
In my opinion NCL had the best production shows, mainly because they are actual Broadway shows and not random one offs just for the cruise line. Carnival by far had the best comedians/comedy shows.
Princess had higher end food options, for example smoked salmon on the buffet for breakfast (Carnival only has it in the dining room). But I think the dining room food on Carnival was superior to NCL. Also the huevos rancheros from Blue Iguana at breakfast are delicious.
On NCL basically everyone has the drink package and they don't have a drink limit (at least when we went), but the included brand tiers/cocktail options are lower than Carnival. Carnival has a 15 drink per day limit which has never been an issue.
I've never really been bothered by the clientele, good people watching. We mostly do 7 day off season though. I think there is enough variety and spaces onboard to make it whatever kind of vacation you want it to be.