Patrick Taylor: I got these diagrams and information from 38 Basic Joseki.
With , Black directly takes the corner. is necessary to prevent getting sealed in. While Black gets both the corner and a n extension, he loses sente with this sequence (though it still looks big to me). White has possible sente plays at a and b
Black uses the double hane of to build a higher position, but White is stronger than in the earlier continuation. Black can also still play at a in either of the two preceding diagrams to take the corner.
Question: If Black does not play from the first continuation, can White jump into the corner? If so, how?