I always go to SIN for business.
Both business and economy classes I have taken. The services are same. For business seat, SQ is better. For economy one, the seat is depending on the aircraft you travel. If the flight uses 777-300, both airlines are same.
SQ’s Airbus 330 and Airbus 380 are new aircrafts.
If you always take CX and the costs have slightly different only, try to use SQ.