I would recommend the Four Seasons. The rooms are nice, the beach is great and the spa very nice. I have not stayed at Banyon Tree but went to visit and it was looking a little tired and this was a couple of years ago. Four Seasons is not my favorite resort in the Seychelles but we certainly really enjoyed it. My favorites are North Island and Fregate Island, but Four Seasons seems to be the best on Mahe. I am sure you will enjoy.