Not too bad (the worse is to come later)

I remember you live on the west coast, so it will not be that long. Kids that age will get excited for a few hours and then spend most of the time sleeping. A good number of young kids, as I observed, were actually hard to wake up when the plane landed. When they get to 2-3 years old they will not sleep as much, then towards the later part of the trip they can become really bored (and uncomfortable with the seatbelt). Make good use of the time during overlays to give the kid some exercise (and exhaust his energy), and take plenty of treats! By all means, get aisle seats so that you and your child can move around.

Now to your question: I think it does not matter much to the child. Select what is more convenient to you.