We have been to all 3 of the Couple's AN areas, and for us, the best, BY FAR, is Sunset Beach at CSS!!
CN - A small area; no pool; gets very little breeze because of the hedges on the side for privacy so it gets very hot in that area; to go into the ocean, you need to walk across the path of people walking by with bathing suits on; and you swim in the ocean next to those with suits on.
CTI - The island is nice, but has a very small pool, not really big enough to swim in; it seems to be always very windy on the island, some days too windy so it is closed for the day; you have to wait for a boat to take you over; you have to wait for a boat to take you back; there is no place to swim in the ocean off the island, as it is very rocky and lots of sea urchins.
CSS - very private, a beautiful walk by a pond on the way over, a large pool to swim in, with swim-up bar, a grill for lunch, a large beach area where you can spread out and be by yourself if you wish; the beautiful ocean to swim in.
Here is a link to pictures from our 3rd trip to CSS. There are a number of pictures taken at Sunset Beach early in the morning before anyone else is there which will give you an idea of how it is set up. There are also some pictures on there from the island at CTI.
We have only been to CN last March 2012 and we are booked again this year at CN March 9-16, 2013. Last years trip was our first AN experience. Neither of us were particularly nervous about the AN beach due to everything we had read on this forum. The beach at CN is small, but still large enough to seperate from other guest if that is what you want. Our first day we stayed close to the hedges, but found that it did not get much of a breeze. Other days we moved more to the middle of the AN area and it was very nice and breezy and easy to get to the ocean to take a dip. The bar and restroom is in the far corner, but most times the bartender would come by and take our drink orders. The hot tub is nice and clean and a good place to get wet without going down to the ocean. What struck me most about the AN beach was the diversity of people in age, size, personality, and where they were from. Met many nice people there as well as on the other beaches. CSS sounds nice with the pool etc., but for us, we are sticking with what we know at CN.