As we said earlier, the cross-drop is favoured in situations where you hardly get to the ball in the front and flip the wrist in the last second. On the other hand, when there is time to chose a shot (and also to your opponent to read/guess what you are going to do), then you will hold/retard your deceptive straight drop as long as possible, and again, flick the wrist in the last moment, as Amr Shabana does it here against James Willstrop below.
