To my knowledge, A and B are closest to Sunset Beach, but you would only be assigned those if you booked a Beachfront Jacuzzi suite. I'm sure you'll enjoy it whereever you're at. Enjoy.
Building A is closest to SSB. We were in Room A-24, 2nd floor corner, and had a excellent view from our balcony of the pool and watersports area, along with being able to watch the beach party steel drum band playing. Balcony is small, but we spent all our time on SSB as well, and the balcony size just didn't matter. The rooms are great!