I am a big fan of the Hyatt, our family has stayed there 8 times and we have never been disappointed. They have beautiful grounds, including the (imho) nicest pool and water slide on the island. The people who work there are superb and we have always received great service. The restaurants are good, but there are so many good restaurants on Palm Beach, we mostly go off property for dinners. I have not stayed at the Marriott, but have visited. In my opinion, the Hyatt has nicer grounds. The fact that the Marriott has the hotel and 2 timeshares on the property, makes it seem larger and less intimate than the Hyatt. I also feel it is easier to travel around Palm Beach from the Hyatt. It is more centrally located and along the boardwalk that runs behind the high rise area. When we have walked to the Marriott, it seems hard to get to. Again i have never stayed at the Marriott, so cannot give the most unbiased opinion, but i know you would not be disappointed at the Hyatt.