Both cruise lines would fit your age group, but as to which is better has a lot to do with the particular ships you are considering, the itinerary AND if you are traveling with friends or going solo. If you are alone, definitely go with Royal Caribbean! While "free-style dining" has its benefits - it is not a good option for people traveling by themselves.
Nancy made a good point about free-style dining. Perhaps you may want to consider a larger ship, generally more things to do. Our last NCL was on the Sun, we had a blast. I took a few books and never took them out of the bag. There was too much to do, had trouble choosing.
I felt the only age group missing from that cruise was in the 20-30 range, other then that, all age groups were well represented, lots in the 30-40 range. Get out, meet people, have fun.
I have sailed on both R.C. and Norweigan Cruise Lines and can honestly say that I am a R.C. man. Norweigan was a small, older ship that attracted a lower class (sorry!)type of passenger. Also, once the dinner and show was over, Norweigan was settled down and tucked in for the night...and I am talking 11:00 P.M.!!!!
Absolutely NOTHING going on at night...
R.C. is by far the class of the sea all the way around!!!
Hope that helps!
I was not really impressed on my NCL cruise back in 2000. The Freestyle idea sounded good on paper but in practice we hated it. We ended up at a table for 2 almost every night since there was a wait otherwise. We did not realize how much we enjoyed the camaraderie of the same tablemates and wait staff for the whole cruise untill we tried Freestyle. I also felt the service was subpar as all tips were pooled. Finally, I was in my early 30's and felt that the ship (the NCL Star) had attracted an older crowd, at least on our cruise.
The ship was fine, the itinerary was fine, we LOVED the art auctions (of all things), but the Freestyle dining and the ship going to bed at 11pm basically made us think we won't be on NCL again.
I like RCI but they really don't cut singles any break at all so my next cruise may be Carnival