I know in the MLS you see the foul signal from the AR and movement down to the corner flag for a PK whereas over here in the UK we use the traditional foul flag and across the chest for a PK. Different countries to vary ever so slightly with how signals are. As an example of another thing that can differ, if there's a foul by the AR that the AR feels is worthy of a caution I prefer a hand on the front of the shorts by the pocket rather than being called over as it draws unnecessary attention to the AR, if the foul is worthy of a red I instruct the AR to put the hand on their back shorts pocket. It's preference really on what people like, if I went over to America and refereed with NAR's I'd leave them use their native PK signal so not to cause any issues where as if they came over to the UK I'd expect them to use the flag up and across the chest. As I said it's all down to preference!