I believe the surrounding waters around Conrad is better too, and teeming with marine animals - so if you are more of a diver/snorkeler, then South Ari Atoll where Conrad is located will be more appealing to you. See whale shark etc.
But if you have zero interest in water sports, and will be staying inside the villa for the majority of your time, then you will probably enjoy StR more and the pampering.
Different strokes for different people.