Dawn Beach is right next to OBBR, not a long walk at all. There are a few places to eat. I think it would be much quieter at night.
SBR has it's own man made beach if you do not feel like leaving the resort. One problem you may have is the walk back up the hill from the beach to the A, B or C buildings. I am sure you don't know where on the resort you will be. We used to own there when it was Pelican Resort and we were in the C building. At the end of a long beach day, the walk up that hill can be tough.
That being said, I would still choose SBR. There is much more to do in the area. Many more restaurants. And you are renting a car so getting to the many prettier beaches SXM has to offer we be an option.
Just my own 2 cents. Whichever you choose, enjoy your stay. Have Fun
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