I used to fly AA a lot, and occasionally get stuck on it, I don't like the airline, but its top elites seem to be quite happy with it. I am mildly content with DL and they fly where I need to go. Two years ago I would have been shouting DL at the top of my lungs here, but after the SWU cutbacks, I still favour them and think the programme is pretty good, but it used to be miles ahead of AA.

4 important DL advantages that are better than AA

1. You get six PMU's per year as a PM, rather than four that you get as a top at AA (although the AA ones can be used on lower fare classes.

2. Free CRC membership.

3. As a PM you get unlimited 800 mile upgrades, while at AA you earn them as you fly. The upgrades are available whenever you book your flights as opposed to other levels and airlines where there are hour deadlines.

4. They are 800 mile upgrades rather than 500 mile upgrades, so you get more bang out of them (of course they are not useable on the bottom three fare classes).