Yep, I've been to the D.R. more than a few times. Taken my kids every time too (they were 5 and 8 when we started taking them there). But that was BEFORE I went to the Mayan Riviera. I really have no need to go back to the D.R. after discovering all that Playa has to offer. The only way I'd be swayed to go back to the D.R. over Mexico is if the trip was free...or close to free! At the places we stayed, the beaches couldn't compare to those in Playa.
To be honest, and I think it might have had something to do with WHERE we stayed, the beach reminded me of home, right here on the Joisey Shore. The sand wasn't as white as MX, ocean not as clear or blue as MX either.
And nothing beats the ability to leave your hotel whenever you want. There are so many UNESCORTED things to do in the Mayan Riviera! Just having a town to walk around is so worth it. You have nothing like that in the D.R. Well, then again, if going to La Romana, you do have the town of Altos De Chavon, which is a really quaint Mediterranean village...but it's not Playa!
Of course, you'll have to continue your research, we're all just giving you our 2 pesos (as Denise says!), only you can make the final decision. Just be careful, I fear you may be headed for analysis paralysis
And for some, there's no return, just endless confusion!