31A is my favorite seat as I travel the JFK-HKG-JFK route quite a lot, and trust me, it's the best seat. Don't forget that this is a 16 hour flight, and there is nothing really that interesting to see outside... comfort is key, and 31A has everything. You can lean against the wall and sleep with as much legroom as you could possibly want, while being able to get up and go to the bathroom (which is right in front of you). A FA will sit in front of you during take-off and landing, and I've had a few chats with them before.

31B is a middle seat which doesn't offer you anything to lean against to sleep, and 31C is actually quite a bad seat because of the amount of people walking to the bathroom and lining up, and is a seat I usually avoid. Let us know what you think after the flight!