The Greek term ek pouresthai has a connotation of origin, but the Latin term procedere does not. The ab utroque procession of the Holy Spirit confuses the Father with the Son and creates a type of semi-Sabellianism.
The Son's sending of the Holy Spirit and the eternal procession of orgination are two completely different things that the Latin fathers failed to understand because they could not read Greek.
The ab utroque procession of the Holy Spirit also undermines the Father's place as the unique source of the Godhead (St. Basil the Great) The Son is not the Father and the Father is not the Son.
Also, the Augutinian idea that the Holy Spirit is the love between the father and the son depersonalizes the Holy Spirit to the level of being an impersonal force.
St. John of Damascus said the Holy Spirit is "the Spirit of the Son, not FROM the Son."
If the Holy Spirit proceeds from the father and the son as it from one principle, then the Father and the Son therefore lose their personality and distinction.
Ah, but that's where the Theotokos comes in! She has three relationships to the Most Holy Trinity: the Most Favored Daughter of the Father, the Mother of the Son, and the Spouse of the Holy Spirit. Her relationship with God was most intimate and personal. As Christians, she is the example of what is possible with God - everything.