Be aware that on the A380:
1. Exit row seats are a bit narrower, because the TV folds into the arm-rest
2. The folding TVs are a bit smaller than all the other TVs
3. The TVs have to be moved into the armrest during takeoff, landing etc

Of course, you do get a lot more legroom. Also, some exit rows have bassinets for babies - make sure to ask for a row without a bassinet at check-in.

All JFK flights use the A380. For HKG, it depends on which flight you're on.