" Aren't Panagia and Immaculate two sides of the same coin? One emphasizes the positive, All Holy the other emphasizes the complete lack of negative, without sin."
I suppose one could say that. Both terms are used in Orthodoxy. I have not heard the appelation "Panagia" used in the Latin Church, but I suspect it is also.
As K points out, the Greek equivalent for the Latin-based word "immaculate" is used very often in Orthodox liturgical texts for the Theotokos, as are positive appelations.
Because of an understandable (but in this case inappropriately placed) desire to avoid association with the doctrine of the Immaculate Conception, this word is often translated as "most pure." For instance, the most commonly used OCA translation of the hymn to the Theotokos sung at the Divine Liturgy at the end of the Anaphora says "ever blessed and most pure and the mother of our God."
The "most pure" is really better translated as "immaculate" or "blameless", because the Greek original has the absence of a negative. Of course in this hymn and elsewhere in Orthodox liturgical texts, the Theotokos is referred to as "immaculate" because she didn't commit sins during her life, not because of anything surrounding her conception.
The services tonight for the Nativity of the Theotokos were beautiful, filled with references to Eve rejoicing at the birth of the woman who would undo her tragic sin, making possible her own deliverance from Hades.