They are the exact same flights. The first/cheaper one is just booking the domestic AA segment as the CX codeshare flight number, while the second/expensive one is booking it as the AA prime flight number.

There will be different LP earning, the first will earn as two CX flights (based on whatever fare code each segment books into). The second would earn as an AA flight + CX flight.

Even without knowing the fare codes, I can all but assure you that any few additional LP's you may earn by booking the second/expensive itinerary will in no way be worth the $500+ price delta.