Flying Fish. No contest. Their menu is consistently innovative and interesting, and they have a much better location and ambiance. I was very impressed with my last meal there, and I would tout it as one of the best restaurants on property.
Narcoosee's, on the other hand, is disappointingly mediocre. With its prime location and prestigious home resort, it could and should be so much better than it is. Instead, it is hardly worth its signature level pricing, and it's definitely not worth two table service credits, especially when there are so many better 2 TS options in WDW on which you can dole out those points.
As for your party's dilemma of needing both safe and exciting menu options, Flying Fish definitely has great options for the seafood lovers, but I'm told that the steak option is also very good.