Gwilmot,

When I made the same decision to go from Delta to AA (a bit over two years ago) my travel agent did the legwork. As well as having an inside track to find out who to talk to, she had an AA sales rep who knew how much business her agency did with AA. I got PLT immediately when she faxed them a current Delta statement showing the comparable (Gold Medallion) level. My welcome letter also included 4,000 miles (if memory serves) worth of upgrade credits.

Two reasons why comping is better than a Challenge:

1. You get elite benefits, including mileage bonus, immediately - not just on the flight in which you meet the Challenge criterion and beyond. That alone is worth over 10,000 bonus miles for PLT since you'd have at least that many status-free miles to work through before you boarded a flight to take you over 15,000.

2. If you miss out on requalifying one year, you can still Challenge after that. With rare exceptions, you can only do it once, so if you use it to get PLT the first time that's it.