Own and absolutely love both of these. 2 of the best summer fragrances I have.
I am not sure about those saying Blanche doesn't have good longevity. For a citrus fragrance, it has incredible longevity.
I was not able to pick a favorite, so I didn't vote. I suppose if dressed more casually, I would lean toward the Chanel. If in a more formal situation, I would go with the more complex Dior.