Each movie covered the story from slightly different angles. "Flight" focused more on the personalities we came to know through the phone calls that were made on the plane before it crashed. "United" focused more on the events that occurred in the background. It did a very good job in capturing the chaos that developed in such a short period of time on 9/11. Of course it also did an outstanding job in depicting the last frantic moments aboard the plane as the passengers try to retake it from the hijackers.
I know many folks think movies like this came out too soon after 9/11. We didn't really need to see what happened since most of us were watching the events unfold live on t.v. We don't need re-enactments. There were thousands of tragic tales written on that day, but the story of flight 93 is one that will stand out. Both of these movies handle the subject very well.