I voted SQ becuase they are a great way to get around my corner of the world, and I've always had the priviledge of flying J with them, which as most people agree is a model of services standards we like to see in J.
KLM is always high up on my list. Usually unbeatable prices, superb connections from many UK airports, ease of transfer at AMS, the only downside is the definately ordinary J seat and mediocre lounges, but this is more than made up for by the onboard service.
I've said it before and I'll say it again... There is something special when the CSS introduces him/herself when you first arrive at your seat and calls you by name without reference to the list, and all the cabin crew continue to do so for the duration of the flight.
In Y just the prices and easy non Heathrow connections do it for me.