If you are wondering what's the "best beach" in the DR, I'd say any of them. The DR has it all. Each beach with it's main "thing". Water sports, fishing, snorkeling, wind surfing and more.
And lastly, our horseback riding trip lead us to the beautiful beach of Macao Beach. Which had local vendors selling various hard goods and food.
Whatever it is you're looking for, you'll find it here. Whether quiet and peaceful or exciting and happening. The DR will have you covered.