Having been on both lines many many many times, both have their perks. Royal doesn’t have the free at sea, but NCL is often more a bit expensive when you in comparable ship classes and itineraries. Those FAS costs are more built in. nothing in the NCL fleet can contend with an Oasis or Icon class. NCL Bliss is my all time favorite ship, but I was not in awe of it like Wonder OTS. Royal is much better, IMO, for younger kids and families. Coco Cay is vastly superior to Great Stirrup Cay. I’ve had much better service as a regular passenger on Royal, but vastly superior service as a Haven passenger vs Royal Sky Class. Speciality dining options on NCL are a MILE (maybe two) better than Royal. NCL has a better night life.
there are all my personal opinions and observations. Both lines will continue to transport my fat butt around the globe depending on dates and itineraries. Others will call me crazy on some of the things I said above, but that is their opinion as well. Personally I favor NCL with just the wife and I, but favor Royal when we take the kids. I recently booked my first Princess cruise and having a hard time figuring them out, so I feel ya on that!!