The differennce is most likely to do with the flight planning programs that the their respective dispatchers use. With the computer selecting an arrival fix and STAR that is almost never used in the real world. Most of the time ATC accepts the flight plan "as filed" and then the crew gets a new clearance that takes them to a more appropriate fix and STAR as they near the destination. It is also very common at LAX to have approach send you to the south complex when you want the north and vice versa, usually you can then request the tower controller to switch you to a more favorable runway. Happens all the time