This is a regular question here. My opinion, until proven otherwise, is that you must choose the option that sucks the least. I been to three hotels in Singapore and done a site inspection of about a dozen others:
4S: Yuk. One of the poorest 4S's in the entire chain. Dark cave like rooms. Below average pool. Just depressing and unfriendly.
Raffles: Nice pool. Dark rooms. Hostile staff. Total touristy circus. I can't image ever going back.
St Regis. I liked this place. Pool is average. My room was very nice. Big, bright. Don't use the wireless. Breakfast was a terrible buffet in one of the big conference rooms. No restaurant or bar worth mentioning.