The SQ westbound flight is great if you want to be in Manhattan early for some work. The SQ eastbound is at 8pm, which is OK, but you are pretty certain to experience the 1 hour taxi from the gate to the runway. The 10pm LH flight is much better, you just taxi for 10 min.

The eastbound on LH or SQ is far too short to get any sleep if you even dare to 'enjoy' the onboard service. Hence the LH flight wins since you can eat in the lounge and then just sleep on board.