Think there are still some differences in Y if you consider quality of IFE, meals & snacks, sometimes luggage allowance.
Perhaps consider, as mentioned above, FF status, if any... But also, the number of stops and total travel duration.
To fly SQ you'd have make your way to one of the cities that they serve in the US. The only one that flies nonstop to Singapore if I'm not wrong, may be from SFO.
Alternatively, some other airlines might be able to get you to SIN with a single stop (e.g. BA, KL, AF, LH, KE, QR).