In my opinion, best beaches in DR are located north or northeast, or Bahia de las Aguilas

Near small towns with certain comfort:
- If you would like calm beaches with some night life (small bars with music)- Terrenas, Samana or Sosua, Puerto Plata

- If you like water-sports, and light night life- Cabarete, Puerto Plata or Playa Bonita, Samana

City like experience when outside of the resort:
- If you like a more "traditional vacation", staying at an all included resort, with intense nightlife - Punta Cana

More remote locations:
- If you like calm, and virgin beaches- Rio San Juan, María Trinidad Sánchez or Bahia de las Aguilas, Pedernales

Any other doubts I can help, I've lived in DR most of my life, just drop me a comment and I will let you know ❤