Depends on the student. Attitude problems are probably the biggest red flag. Lots of students struggle in one way or another, myself included, but how you react to it has a huge influence on whether or not you'll be successful. If you're combative, shift blame to others or are unwilling to ask for help, it'll be difficult to get through. But occasionally we have students with fantastic attitudes who get extra training but it just doesn't come together. The Oral is more of an issue on the 747 side, they're a little more old school and want you to know the nuts and bolts of the airplane more. The simulator footprints are similar - we don't have AQP so it's the maneuvers-based check ride with the requisite demos during sims. If you don't have jet time, EFIS time or FMC time, that can be a challenge. They typically ask early on to ID someone who might need a little help. A guy in my 747 class had zero EFIS experience but made it through fine.