Three reasons to go for AA EXP:

1) Miles will count toward eventual 2MM status;

2) More fares are upgradeable (upgrade even when on lowest fares, vs. no recognition and upgrades on LUser fares on DL);

3) If you get stuck in coach, MRTC on AA.

This is especially true if you are on higher fares on business paid travel, but then want to travel on lowest fares on your own leisure travel, but would still like to upgrade while on your leisure travel.

Djlawman