The "best" beach is somewhat subjective depending on your criteria - wave size, amount of activity, quality/type of beach furniture, level of service, ability to do certain water sports (paddle board, Hobie cats, snorkel from the beach, etc.), ability to walk long distances, amount of shade, and of course water color and type of sand.

The original "best" beach in Riviera Maya is Maroma. This was the first luxury hotel built in the area, and still has the best beach beds and beachfront bar. Since it was built prior to the building codes that limited the beachfront development of later resorts like Mayakoba, there are plenty of beachfront and oceanview rooms here.

Xpu-Ha, the beach at Esencia, is beautiful as well with turquoise water and white sand. It offers more privacy / peace than Maroma because of it's location on the beach and that there is less development in the area, but there is no reef. There also are not any true beachfront rooms.

Another factor to consider, especially for short stays, is proximity to the airport. Cancun hotels are about 20 minutes, Maroma is 30, Mayakoba 40, Playa del Carmen 50, Xpu-Ha 60, and Tulum 90. There are no true luxury hotels in Tulum, and none located within walking distance of the action in Playa del Carmen.

Hotel quality will be similar in any of the destinations the OP mentioned. The primary differences will be the the "swimmablity" and quality of the beaches and water, and the off property activities.

I just did a quick two nights at Viceroy Riviera Maya and I was very impressed. The F&B was the best overall that I have experienced in the area in twenty plus visits over the past eleven years. There are oceanfront and oceanview rooms. It is also adult's only. The beach is not nearly as good as Maroma or Xpu-Ha, but it's proximity to Playa del Carmen is a plus for those wanting to go out at night.

I spent the entire month of April in Riviera Maya. It's an area I love and return to again and again for the great luxury hotels, high service level, amazing cuisine, and access to culture / history. After eight days straight of rain in Boston upon my return, I am more than ready to go back