If you are considering AA, then make sure and sign up for the Gold or Platinum challenge. You will will have Gold status after one trip or Platinum after 2. Go to the AA forum and read the sticky at the top. AA counts any miles earned, flight, credit card, hotels, etc toward the lifetime gold or platinum status.
After gold, your first RT, you would have access to international lounges even when flying coach. This can be a nice perk.