Waikoloa by far. Towers lounge has free mai tais!! Love the boats at night. Usually you can find a private hammock for 2. The gardens are to die for. In the nearby shopping center (free shuttle), eat at Roy's.
I wasn't that crazy about Rome's Hilton. I had been dying to stay there but found it very hard to use public transit and extremely expensive by cab. It is located very far from all the sights. Sundays the shuttle shuts down (very religous hotel..). And it was not deluxe enough to make up for the inconvenience.