We stayed at CN back in 2008 in the deluxe garden. I had read a review prior to booking that said all the rooms were comparable and it really wasn't worth paying for an upgrade. We were further from the beach than some of the rooms, but not enough that it mattered. We spent very little time in our rooms and most of it on the beach. We are going back and staying at CSA in June and I again just booked the basic room. I hope I get as lucky as I did at CN.
My understanding is that a Garden Suite is basically two Deluxe Garden Rooms with the wall in between removed. This allows the Garden Suites to have a much larger bathroom (double vanity, Jacuzzi bathtub & separate shower), a sitting area and a balcony twice the length of the Garden rooms. The longer balcony allows the Garden Suites to have a hammock out there. Hors d'oeuvres are delivered each evening to the Garden Suites. You may also have dinner delivered to the Garden Suites if you would like an in-suite dining experience.