If you go to the stop in Santo Domingo Maximo Gomez, you have the choice of Aptpra or the Expreso Punta Cana buses, the offices are a few doors apart, and I prefer the Aptpra buses as well. If you go to Parque Enriquillo, Aptpra has a terminal on one side with a lot of departures to Higuey, La Romana and also their Punta Cana service, and Expreso Punta Cana operates from a different office on the other side of Parque Enriquillo. Then the Aptpra makes a stop in SD Este and the Expreso Bavaro makes a stop in a different place in SD Este, and then they both go nonstop to Punta Cana airport, and after that I have no idea where they go as I have only ever taken them to the airport.
Anyone who drives along the highway from Santo Domingo to Bavaro must have noticed the silver and blue Aptpra buses there are a lot of them.