You are asking us to make a difficult decision. These are both very enjoyable dining experiences, although they are also very different. Yachtsman is more formal (but still family friendly). We had a table that looked out over the pool and toward Crescent Lake, so the view was very nice, particularly at sunset. They oak grill there, and I got the ribeye which did not disappoint.
Narcoossee's is more informal and does have an unequalled (closest) view of Cinderella's Castle and the Wishes fireworks for a dining venue. The non red meat selections are better, so we tend to eat there more frequently becuase my wife doesn't eat beef.
As with any dining choice, factor in the touring plan you are putting together and consider whether or not going to one of these will give you an opportunity to see things you'd otherwise not. For example, after eating at Yachtsman, we go to Boardwalk, walk around and catch what you can see of Illiminations then go back to our rooms. After eating at Narcoosee's, we walk around the GF, grab a nightcap in the lobby and then go back to our rooms.
Don't think you can make a wrong choice, but you can make a more right choice regarding the rest of your plans.
We also love their almond cheesecake.
Yatchsman while OK, didn't seem to be any better than many of the steakhouses around here. Although to be fair, I live in Texas where good steaks are easily found. Yatchsman does have an excellent seafood salad appetizer though.
