I haven't read all the replies yet but wanted to add my opinion based on my families experience. I would take business for the way home. (eur to us) The transatlantic nighttime really isnt' bad for a little kids - they are small, mostly will sleep in your lap no matter what as it is night time for them.
The return however is different - my kids are always awake. We needed the space when they were little - my dd never slept on our returns and was somewhat active (coloring, playing with stuffed animals, eating) I really appreciated the extra space as I was awake too!
Happy travels.