We tried both of these restaurants for the first time this past October. I can say I am more likely to return to Jiko next year. I generally do not complain about the price of food, but Narcoossee's for what it was, is a bit overpriced.
We were a little unwhelmed by the food, but to be fair we also ate at Citricos, California Grill, Yachtsman Steakhouse, Il Mulino, Artist Point this trip-pretty stiff competition. I feel Narcoossee's was about average for us.
Jiko, with the exception of a whiny kid sitting next to me, was more peaceful. My DM, the picky eater, was content with her meal. The bbq chicken flatbread was excellent, the other appetizers (corn soup, salad, cheese plate) were great and the entrees were exceptional (halibut and filet with mac & cheese).
The setting for Jiko is a little more adult oriented, whereas Narcoossee's had more children. Without a car Jiko is a little more difficult to get to or from depending on where you stay as well.
I would say if you like to be adventurous and are open to new tastes I would try Jiko.
I hope you enjoy either choice