I have cruised with Carnival, Royal Caribbean and recently with Norwegian.
I went on Norwegian because I was interested in the Free Style cruising. I loved the idea of eating with who I wanted when I wanted to eat and wearing what I wanted to wear. After all I feel if I'm on vacation I should be able to do what felt good to me. I've never liked having to sit with strangers, or having to get dressed up on my vacation. I was very impressed with the food on Norwegian. It was also wonderful to go to dinner dressed comfortably. However, the ship did not compare to Royal Caribbean. It was kind of closed in, it wasn't open like Royal Caribbean ships. I felt a lot of that was because of all the different places to eat. This was a great feature but I think there could have been a better design when building the ship so that it didn't feel so partitioned off.
The entertainment was not at all on the same level as Royal Caribbean. Since this was only a two night cruise I'm not sure if this was an accurate representation of what the entertainment would be on A 7 or 9 night cruise but I don't know if I want to take the chance to see.
Boarding and disembarking the ship on Norwegian was a breeze. Royal Caribbean really needs to take lessons on that.
I felt that I would be bored on the Norwegian ship for more than a couple days. At night, there didn't seem to be more than one form of entertainment at a time to chose from.
In conclusion I feel Norwegian had a lot of positive things. Some more positive than on Royal Caribbean, (ie the food, embarking and disembarking & the free style part) However, the entertainment & ship really makes my selection of who I like better. As much as I loved the Free Style cruising I don't think I will cruise with Norwegian again. Royal Caribbean's ships and entertainment win out for me.