What's the difference between brioche feuilletee and croissant dough?

They are very similar, here is the difference according to The Bread Bible by Rose Levy Beranbaum:

Croissant and brioche have the same ingredients: flour, yeast, salt, sugar, milk, and butter. There are only two significant differences: croissant dough contains almost double the amount of butter and has only milk as the liquid component, whereas the liquid for brioche dough comes mostly from eggs, with only a little milk. The eggs in the brioche dough give it an airy cake-like crumb, while the large amount of butter in the croissant dough, and the way in which it is rolled and layered into the dough, gives it its flaky crumb.