Only that Punta Cana does not have much good day trips outside of the resort for bigger kids. And hotels there generally do not have as many activities, like mini-golf, kids club, ping-pong, game room,etc.. Hotels tend to be smaller than Mexico and Cuba ones.
Among all 3 three countries, Cuba, Mexico, Dominca Republic, I like Mexico the best. Mexico also has the best food, then DR, Cuba is the last. Mexico also has most choices for day trips.