Beauty queens can be arrogant, even in torah text.
Leah brings beauty and smarts to a level that Rachel can't conceive.
Do you buy cereal because of the box or because of the way it tastes inside? Of course, you buy it because of its significant flavor. Leah is beautiful on the inside and Rachel is ONLY beautiful on the outside. Perfection is going beyond in all compatible standards, not just only in the standard of beauty. Leah may be weak in the eyes, but Rachel is weak all around. Complexion and body size could be perks to the package. But without those, Rachel has no package. Leah is the one for Jacob because of her impeccable inner-self.