Best Cross Resort Privileges in Punta Cana/Bavaro?

I have been to the Iberostar Punta Cana, which is next to the Iberostar Dominicana and would go back. Haven't been to the RIU complex..yet! but they have like 4 resorts in one I believe.

I've been to RIU, (RIU Palace Punta Cana), and you can wander the various properties, (were 4 or 5 in a row back then), BUT you can't use the facilities of the more expensive properties if you're staying in a cheaper resort. In other words, you can always trade down, but not up. I assume the same rules apply to the other brands. If you check out their websites, you can probably find the answer for any specific property.

Gran Bahia Principe resorts
Barcelo Bavaro resorts
Most of the resorts are so big and well equipped there is no need for cross-resort use. Dreams Palm Beach is an example of a great family, stand-alone resort. Hard Rock hotel has 1800 rooms and the facilities to cater for them.

There are only few "multiple resorts" in one, most of the other resorts are just twins that somehow are categorized as two different resorts but are same.

Example multiple resorts:
Barcelo Bavaro (Palace & Beach)
Fiesta Palladium (Bavaro, Punta Cana, Palace)
RIU (Pallace bavaro 5*+, Palace Punta Cana 5*, Palace macao 4*+, Bambu 4*, Naiboa 4*)
Iberostar (Dominicana 4*+, Punta Cana 4*+, Grand Bavaro 5*+)
Majestic (Elegance 5*, Colonial 4*+)
Princess (Caribe Club 4*, Tropical 3*+)

Twin resorts (basically the same thing, one or two receptions but the same facilities). usually one resort form one side of the road to the beach, and the other resort from the other side.
Melia (Caribe, Tropical)
Ocean (Blue, Sand)
BeLive (Bavaro, Punta Cana, now merged)
Bahia Principe (Bavaro, Punta Cana)
Hard Rock (don't know the names, so let's just call it the first and second)