I’ve only stayed at Amanpulo, so can’t comment on Shangri-La Boracay. Does R&R include prioritizing privacy? Because Amanpulo delivers that. We stayed for a week over Chinese New Year when the resort was at full occupancy and we rarely saw anyone in “our” beachfront.
However, as a late 20’s couple into R&R, I would say that we decided the price wasn't worth it (or worth coming back) for a few reasons:
(1) We’re not major ocean swimmers, which means the perfection of Amanpulo’s pristine waters are a bit wasted on us. Plus, as beautiful as white sandy beaches are, the glare makes it hard to appreciate even with sunglasses for too long! In retrospect, we probably would have enjoyed a private pool villa over a beach casita… but then we could be at any good resort, and no point in going to a private island with one of the most beautiful, uninterrupted beaches in the world.
(2) It was pretty hot and sunny, so we spent most of our time at the Beach Club, which had more shade than our casita’s lone umbrella. We really enjoyed the Beach Club (comfy lounge chairs, good music, food & drink at our fingertips), but we weren't exactly taking full advantage of our casita’s privacy and seclusion.
(3) Our idea of R&R is pretty inactive (card games, reading & spa time), but we enjoy interesting excursions to punctuate the long stretches of R&R. Amanpulo is pretty limited in activities and diversions if you’re not big on water sports. And you certainly have to spend more to do more.
(4) We’ll give some allowances on food quality for remote islands, but the limited dining options with average food keep us from considering another stay.
Re: legendary service, I think other Aman properties imbue more local culture and character. You really just go to Amanpulo for the beach and privacy. The service is great, of course, but if you’re at your villa/casita most of the day, you’re not going to feel/see the service that much.