While it has been a couple of years since my last stay here, I will say of the Marriott choices in Cayman, the RC is easily the nicest and most luxurious. If given a choice, I would easily stay here every time, but I know some prefer the Westin. I don't know that anyone has said they prefer the Marriott over the other two though.
If you want to see posts comparing the 3 properties check out the
Marriott Bonvoy hotels in Grand Cayman thread.