Havent got chance to try RC Millenia Walk although I visit the area very often (their non participation in RCR makes me prefer to book other hotel)
Raffles seems to push back their opening times to mid 2019
St Regis ... while I stay here often, their service sometimes are quite below expectation
Never try MBS but the massive size of the hotel puts me off .... feels like staying at Las Vegas huge resorts
The FS Sg, somehow all my Singaporean friends hate it.
The Fullerton hotel .... its actually very nice building.
edit
Planned to visit SG this December and try the new Kempinski ... but some unplanned events makes the visit impossible.
Maybe next time