I am also considering going with NCL as I have only sailed with others. The last 2 cruises were with Celebrity however the atmosphere was subdued probably due to the age of the passengers. RCL had a ton of kids that plagued the dining experience from time to time, while Carnival was more fun, but had more emotions that seemed to bubble up to the surface. I guess I'm looking for that happy medium.
Good luck in your search and sometimes I guess you just need to experience it for yourself. Forums like this have members that think very highly of their own opinion while dismissing opinions of others.