SQ doesn't really "offer' their great Y cabins nonstop New York - Singapore, they must configure them that way to make the distance. If they used the usual SQ coach seating, they'd have to make a technical stop. Mind you, it's great for the passenger, and superb service anyway! (Imagine how it would be otherwise, with an 18-19 hour flight...)

Here's the information I've been able to cull:

The A340-500 can carry 313 pax, normally configured; SQ's carries 181 total, only 117 in coach, in 2 x 3 x 2 seats (2 x 2 x 2 aft,) 37" legroom and 20" wide; 9" seatback video screen with 60 movies, 83 television shows, 205 CD albums, 12 channels music and 56 video games, individually selectable. Coach "social area" (aeropub?) Great Circle Mapper says it's 9,534 mi each way and you go so close to the North Pole you might see some new blue ice down there if you look closely.

If you are bi-alliance and in a hurry, you might want to do the SQ flight for comfort if you must do it in Coach.