I’ve stayed at both and like them both, for different reasons.
But, for the same price, my choice would most definitely be for Amara.
More upscale, especially friendly and efficient front desk staff, excellent bedding, rooftop pool, executive floor lounge for afternoon drinks and breakfast (currently closed, I think). I always stay on a high floor on the side with view of the Mahanakhon tower.
That’s the one thing I dislike about the Raya, not only no view but the windows are tiny. Once they put me in a room 1 floor beneath reception and it was quite dreadful. I think it was under a steam room or something. Quite dark and dank. All other times I was on an upper floor, that was ok.