Some years ago, I remember reading a long heated discussion on some forum about how to cross the arms (i.e. if to go over or under the front hand when you move the back hand across to the other side). Personally (sailing B&J/F&W board), I prefer to cross under (like in the clip above). I also think that it is easier to keep the speed if you don't move your feet until you are powered up in the new direction (also illustrated by the clip above), and if you start to step around while you flip the sail (
example clip ) it is more difficult to keep the speed.