Hey, funny you should ask this question, as I will be flying AA70 tomorrow, OCT. 16th DFW-FRA on a 777 and returning on AA71 Oct. 21 also on a 777. Why would I chose AA over LH? Well, the AA777 to me is a far superior aircraft on the inside than the LH 340. Private TV's on every seat. Better coach product with ample legroom, and lemme tell yah, you CAN tell a difference. Try Delta across the pond if you can't. Not to mention, your flight will most likely be shorter on the 777 since it travels at a faster speed than the A340, not by much though. Also, it depends on where your loyalties are. Mine are with AA, therefore I get great mileage and get to keep my gold status. However, I will tell you, I have flown AA, BA, DL, CO, LH, Swissair, KE, UA, CX, and AA has them all beat as far as legroom in economy. Food might be better on some, but when it comes down to it, I prefer ample space.
Ill let you know how the trip goes.
"Bangkok Tower, United 890 Heavy. Bangkok Tower, United 890 Heavy.....Okay, fine, we'll just turn 190 and Visual Our Way