Quick poll: DR or PR??

I'll be going to a wedding at a resort in Punta Cana in a few weeks, and am now arranging my flights. The original plan was to stay at the pricey resort for 3 nights, then hire a car and explore the DR for 4-5 days, perhaps driving to Santo Domingo, before going back to the Punta Cana airport.

But when looking at flights, I realized that I could also arrange a stopover in San Juan. So in other words, I would just go to the DR resort, then straight onto PR for 4-5 days, hire a car and explore.

I need to decide today or tomorrow. We are a 30ish guy and girl, speak basic Spanish and are interested in exploring the old capital cities, as well a beaches, local cuisine, etc. Guesthouses and hostels are ok.

Any thoughts on which will be more worthwhile? Which is cheaper, easier to get around, etc.? Should we go DR or PR?