qantas has recently upgraded their 747's on that route to all be fitted with their award winning A380 seats, so if you could get AA, your flight will most probably be more enjoyable on aa/qantas.
Not sure I agree with that statement with regards to economy class seats. They are designed so that the seat reclines along with the back. This allows them to have less space between rows, and stick more seats on the plane.
The net result is that there is less room between rows, making it hard to get in and out if you are not sitting at the aisle, and there is less room to manoeuvre when using your tray table and seat is upright (such as meal time).
Due to the minimal amount of space, they make the seat pocket so tight that you can maybe get one book or tablet in there.
When flying with child seat, in QF it was right up against the seat in front, whereas in UA there was a couple of inches.
Of course, QF beats UA hands down in many other areas, but seats are not one of them, I don't care about how award winning they are.