I've eaten at all three several times and would choose Citricos. I love, love, love their crab gateau and their steak and pork loin are both good. They used to have the most wonderful berry gratin on the menu, but I haven't seen it there in several years. They've got a chocolate/banana tart thingy that's pretty good though. Narcoosee is great for steak and lobster if you are on the
DDP, although I usually substitute scallops for the lobster and they also have a good almond cheesecake. Yatchsman I have yet to be impressed with. I much prefer the charcrusted steak over at Flying Fish to any I've had at Yachtsman. At Yacthsman I've had the strip, ribeye, porterhouse, and also rack of lamb. I enjoyed the lamb more than the steaks.

They used to have a really good seafood salad appetizer, but it hasn't been on the menu for awhile and I have yet to find a dessert I'd have to repeat there (I've had their sorbet several times, mango cheesecake, and banana Napoleon).
Honestly of all the Signature restaurants I like Flying Fish the most. I love their mussels, cheeseplate, or tomato/mozzarella for appetizers, char crusted steak or scallops for entrees, and any of their dessert trios for dessert. Flying Fish is the only restaurant where I consistently love all three courses of my meal.