The AA 789 hard product is very good. I'd vote better than Qantas, but different people might have different opinions about this. The food is medium--not really different from any other AA business class route. I think Qantas has a better wine list than AA. AA service is, on average, pretty bad.
Overall, I don't think AA vs. QF J on these two planes has a ton to differentiate between them. I'd probably choose mostly on convenience