Lots depends on your FF status. As TWA Platinum, I get 1,000 min per seg, + 1,000 (100%) bonus + miles equal to my fare + 1,000 miles for making Web reservations (2,000 Web reserv. now). So for a 4 seg. short flight, I get about 8,400 miles - of which 4,000 miles are "status" miles.
Don't think I can get same from AA.
And if AA takes over TWA miles 1 for 1, will all end up AA anyway. And status should be equaled as well.
May be opposite if you are High Status on AA and low on TWA.