I flew SQ 380 in Y twice including SIN-SYD but on lower level - the plane was half empty both times so I (and almost everyone else) had an entire row to myself, so in that case better to have 3 seats vs. 2. Huge plane, you can wander both levels for some exercise . For lower level window seats it's difficult to lean against the side-wall unless you have a huge pillow because the wall bulges outward/too far from arm-rest, and also the leg room restricted a little because the wall comes in - I think this is better on top deck. Fabulous experience SQ in general for Y - service, friendliness, magnum bar for dessert , serve-yourself all you want snacks (sandwiches, chocolate bars, fruit, drinks, etc) laid out in the galley, etc... put the usual Y experience to shame.