I'm flying from NZ to the US, via Asia due to a lack of award availability. Currently I have AKL-MEL-BKK-PVG on TG (J) and PVG-DFW-AUS on AA (F). Some CX J availability has just opened on my date (and only on my date) BKK-HKG-LAX. Here are the pros and cons as I see them:

Change:
Change fees to both AA and UA (although I guess I could avoid the UA change fee by just not boarding the BKK-PVG leg).
Four hours in BKK at night when the only lounge available is the not very nice CX one.
Have to clear immigration/customs at LAX (I'm assuming DFW is less stressful).

Stick with what I have:
Nine hours to kill in Shanghai in the middle of a long journey.
More segments--> more possibilities of missed connections etc.
Miles cost is more for F than J.
4-8 hours longer travel time.

I've flown the BKK-HKG-LAX route on CX J before and was pretty happy with it. There are a lot of negative reviews out there about AA F, but I've never flown F before so I might not even notice that it isn't a great F product.

What would you do?