If you're going to upgrade to F (pretty easy most days of the week), then AA is the way to go.

If you connect in NRT, you have a long layover and don't get into PVG until 9or so. If you fly direct, you should be in your hotel by around 5.

To me, it's a no-brainer. AA in J upgraded to F. To me, this is a great use of a VIP or 25K miles.

Also, if you are elite with AA, you don't get the bonus miles on JAL but do on AA.