Frankly, I don't think there is a great deal in it. Seating in Y--and let's face it, that's the key issue--is pretty standard across the board.

SQ does have seatback video in Y, but the equipment on SIN PER might not offer it.

I think I would route with whoever is likely to operate with the lowest load factor--and that mitigates against SQ. SQ sell so much deep discount traffic in the back, that they often operate very full.

Also, SQ does not give you Silver Kris lounge access in SIN if you are flying in Y (only SQ PPS). All other *Gold go to the "Premier" lounge, which is a contract facility.