I regret I didn't clearly explain the most important idea in my previous message. AA may be the best for upgrades today but there is no way to predict how AA's program will have changed in a year or two when you plan to redeem. Accumulating Starwood Preferred Guest or Diners Club Rewards points gives you the flexibility to transfer to AA, or many other airlines, when it is time to redeem.

You can receive a bonus for activating the Citi AAdvantage card, but there is also a bonus for activating the Starwood Preferred Guest credit card. If you are confident that AA is the program you will use you could apply for both. Use the Citi card to earn the bonus and at merchants who do not accept American Express. Use the SPG card to earn another bonus, and as your primary card for spending because...

Citi spend $20,000 = 20,000 AAdvantage miles
SPG spend $20,000 = 25,000 AAdvantage miles