I spent time last week (ie. eating meals and walking around) the Halekulani, Kahala and RH and, without a doubt, the Halekulani was a major disappointment. Almost every inch of the grounds were used and the beach was nonexistent. Regardless of the level of service and luxury of the property overall, a lack of beach in a beach locale is a killer, IMO.
The Royal Hawaiian was surprising because it is smack in the middle of Waikiki, right next to the Sheraton, but it was very quiet and peaceful as soon as I walked through the gates. The decor and architecture exudes restrained luxury. The back lawn and beach areas are quite large and the food looked great (did not eat here).
The Kahala was simply amazing, though it is not in the middle of it all. Great beach, fantastic service and very quiet location.