I am at platinum loyalty status on Princess and Diamond on RCL and have sailed both in the last two months. Below is a comparison of these two lines
Pre cruise
Apps… both are easy to use, with RCL having a few advantages
Rcl allows you to book a future cruise, has frequent sales on shore excursions and packages. You can use your on board credits for these pre cruise purchases. Princess has fewer sales excluding the drink packages
Princess gives Elite members 50% off the internet packages pre cruise. RCL has frequent sales but is still very expensive compared to RCL. You get one day free at diamond level and 2 days at diamond plus. You can gift the free days to another passenger or use it on an additional device.
Check in is equally easy and you pick your time Embarkation
Both supposedly have check in times but I have yet to see it enforced. Neither offers special service to its loyalty members for faster checkin
Both are equally fast for checking in at about a 20 minute wait in Florida ports.
Internet is so easy to use on RCL, however I always have to get help on Princess to get it to work.
Only Princess offers lunch in the dining room after embarkation.
Rooms are ready at about 1:30 pm on both
At sea
Cabins
Both lines have nice cabins about the same size
Rcl frequently has plumbing and air con issues. Even cleanliness issues. They will change your cabin and offer Future cruise credits of 10 to 20% if it’s really bad. I have experienced issues on my last 3 cruises thus why I am back on Princess
Showers on Princess are smaller with a curtain and fixed shower head. RCl has shower doors, larger shower. On Quantum class no clothesline in their showers. on both getting a hot shower can be an issue, as warm or scalding are often the choices
You get free unlimited laundry on Princess at elite level and only one bag on 5 day cruise or longer at Diamond plus.
The beds are hard on RCL even with a mattress topper. I requested a double mattress topper on the last cruise. Princess has the most comfortable beds at sea.
Princess services the cabin twice per day and RCL once.
Both provide Robes on request .
Princess has free movies in the room. RCL does not
Overall Princess wins on comfort of cabin.
Dining
Both have decent buffets and main dining rooms. I frequently have to ask for my entree to be served hot on RCL. Menus on both have not been updated in several years. As always there will be some great dishes and some awful selections. RCL always has Indian food option on their dinner menu. Princess does not.
Both buffets repeat the same cheaper options daily for breakfast and lunch. Since food is not my thing I don’t do the speciality restaurants.
both offer one lobster per cruise per person in the main dining room.
Activities:
Princess has enrichment talks and RCL does not
Both have several sessions of trivia. Princess has better and larger venues for trivia
Princess has more pools, but RCL has slides and larger areas for kids
Entertainment
Both have both production shows and typical singers acrobats, comedians. Nether are great. But you will have some excellent shows and some bad shows
Music around the ship similar.
Hope this helps
Marcia