You didn't say how long you were staying, nor if you have a Carlson Visa. If I had the Visa card and was reserving in the next day or so I would seriously consider moving hotels after 2 days. Book Mercer Street location for 2 days (50K) then Mayfair for 2 days (70K). Four days in 2 nice but slightly different areas.

Otherwise, the Mercer Street location has been my preferred location, though I stayed at the Leicester Square hotel and got a nice King room... I have not gotten a King room at the Mercer Street hotel.