You should check the schedule to see which flies during the day. Red eyes are more tiring.

Generally, it is less tiring to fly westbound due to the body clock being slightly longer than 24 hours.

The funny thing is if you fly Singapore Airlines on your "westbound" itinerary, the JFK-SIN segment may actually be JFK-SIN-FRA! If you break it up as JFK-US west coast, I would suggest JFK-SFO then SFO-HKG-SIN on SQ or CX based on the schedule. I flew LAX-SIN and it arrive a bit too early (6 am). The noon-ish SFO-HKG-SIN arrival time is better.