I prefer to book directly. As a first time guest I book through the reservations department by telephone or email. Otherwise, if I have a contact at a hotel or resort I usually contact that person directly.
I find Aman's reservations departments, unlike many other hotels and resorts, to be a pleasure to deal with. All of my questions are thoroughly answered, and information about packages, rates, and activities have been promptly emailed to me. I feel no need to book through a third party.