Depends on what you are planning to do in Singapore. Bugis is closer to the tourist destinations (Marina Bay, Gardens by the Bay, Haji Lane, Arab district and Little India). And the Andaz is right over the Bugis metro station, so you don’t have to go outside. It’s a nice station with lots of little restaurants and shops.

the Grand Hyatt is on orchard road which is the main shopping district in Singapore. It’s a large stretch with endless shopping malls and restaurants.