Not so clear, depends on metrics and what you are trying to minimize. In miles AA normally costs 50,000 miles flown, in the challenge that drops to 20,000 miles or 10,000 qpoints. But on QF it is possible to earn QF Gold (OW Sapphire = AA Plat) by flying as little as 3000 miles (without a challenge). QF status is not based on miles, but on "status credits" (these very loosely equate to revenue for QF). And the non-AA Sapphires are worth more than AA Plat (at least for those who travel a lot on AA) as they provide free AC access while Platinum does not.