If you have the American Express Platinum card, you can use the two groups they have on their travel website, "Hotel Collection" and "Fine Hotels & Resorts". Once you filter with those two groups, the reservation goes through American Express, and my experience is that any other hotels on their site that is not in one of those groups, they do use Expedia Travel. If I do not use one from those groups, I then go to Hotels.com to find a hotel and then I check the hotel website and almost always book directly through them.