The extra baggage allowance benefit for Silver is quite generous and can be worth a lot of money at times. For example USA-Oz you get an extra bag of 32kg (for a total of 96kg of checked baggage). Do that once a month and you have over thousand dollars of benefit. And the best part is that both AA and AS honour the QF benefit for connecting flights (so you avoid baggage fees on the domestic US flights as long as it is connecting to QF).