Just had the best customer service at the SGS, which is one of my favorite hotels in the world, but did not even stay there this time. I had reserved a room, but my flight got cancelled and I was stuck in Tokyo. Called the SGS at 11:00 p.m. and they said as a courtesy to a Platinum they would let me cancel without penalty. Now that is service. The airline put me up at a miserable airport Hilton. What a letdown from the great hotel I was expecting. Too bad I did not get to stay there as I love the place. Beautiful decor. Often upgraded to a suite and when not upgraded, I usually get an apology for not being given a suite. I think the SGS holds its own even compared to the Peninsula.
The Westin is really nice too. Stayed there once very recently and only got an upgrade to the Executive Floor. Room was very nice though. The electronic controls near the bed similar to the Peninsula. Best part was the Executive Lounge. Must say the evening buffet was one of the most elaborate I have had at any hotel in the world. Service in the lounge was top notch too. Only complaint is the WiFi is difficult to set up. Difficult configuration.
The nicest thing about the Royal Orchid is the view of the river. Usually get a suite upgrade. Not as luxurious as the SGS and the Westin, but still nice. Good lounge.
Try to split your time. You can't go wrong with any of them.