The flaw in this question is that it judges "the hijab" according to the hearts of the women who wear it or those who don't. The one who decides is Allah, and that's obvious... but then again, that's why Allah ordered women to wear hijab. Allah says (in meaning) "the dress of Taqwa, that's better" and in many places in the Qur'an Allah orders women (AND men) to wear proper clothing and cover their Awrah ( could be translated as "naked-ness"), and the hijab for women is an example. Thus, if this question aims to say that a woman who does not wear hijab is not neccessarily bad (or that who wear is not neccessarily good), then the whole logic of the question fails since we talk about an order by Allah, not a person and his/her manners and/or heart.
So, generally, assuming that the woman is wearing the hijab willingly, that woman is more pious yes. Pious means Taqwa, and taqwa means seeking shelter (with Allah--by following the path, or Al Siraat Al Mustaqeem) from Allah's anger. It could be in 2 ways: either disobeying Him by doing that what's not acceptable, or disobeying Him by NOT doing that what is ordered. So, who wears a hijab does what she was ordered to do, and does it willingly for Allah, not to please husband or family, then that's more Taqwa... more pious.