Rebekah was, in a way, a spiritual woman. When she felt her babies jostling in her womb, she checked with God what was happening. Also, she took the Lord's answer seriously - she did not forget it even when her sons had grown up. Later she was instrumental in helping Jacob deceive Esau. How she helped Jacob was not at all spiritual.
Isaac was a spiritual man. He prayed for Rebekah when she was barren. The Lord answered his prayers.
He blessed his sons - he wanted to impart spiritual values on his sons.
The question here is who is more spiritually SENSITIVE, not more spiritual. I struggle with the fact that Isaac was NOT spiritually sensitive enough to discern that he was blessing the wrong son! Then again, I have to recognise that he was blind and very old. I dont think I can say that rebekah is spiritually sensitive. If she were, she would not resort to such an underhanded way to deceive her own husband, help Jacob steal from Esau and cause a rift between the 2 brothers. She remembered the prophecy over her sons but like her mother in law, Sarah, she felt she "had to help God".
Jacob understood the spiritual blessings attached to the birthright. He valued the prophecy that was spoken over his life. That was the evidence of Jacob's spirituality. Esau on the other hand was confused. At first, he despised his birthright and he sold it. When he found out he has lost it, he became devastated and he begged his father for another blessing. By asking for another blessing showed a hint of spirituality in Esau.