The difference between bread flour and pastry flour is that bread flour has more gluten. The pastry flour tends to produce softer crumb, while the crumb of bread flour is “pullier.” “General purpose” flour falls somewhere in between. I have substituted each for the other with no ill effects.

For my challah I use a hard red winter wheat flour (which is fairly high gluten) and supplement it with extra gluten because my wife likes really pully challah. We are rippers, not slicers, and she likes challah that can put up a fight.