The Western view is more reasonable because it has a lot more theological and philosophical explanatory power, whereas the Eastern view lacks this explanatory power. Since the Spirit proceeds from the Father and the Son is begotten by the Father how do we distinguish them? One might say that they have different contingent relational properties such as the Spirit is the one who sanctifies the church or that the Son is the one who purchases our redemption, etc. The problem is that these relational properties are contingent and as a result they just happen to be the case but they don’t have to be the case. They do not tell us anything essential about the Son or the Spirit, they are only accidental relation properties. So for example, in a possible world W* where there is no creation what do we really know about the differentiation between the persons of the Trinity, specifically the Son and the Spirit? Nothing! And that seems like a very strange and odd thing to say about the persons of the Trinity in whom we are supposed to know and love. The East recognizes that there is a difference between "procession" and "being begotten", but how can they explain this? They would say that at least they are both coming from the Father in the sense that their personhood is being sustained from all eternity past. But the question that has to be asked is: Where is the difference between these persons? They could say that it is just mysterious and the causation must be different but we just don’t know how to reasonably distinguish them. This view seems completely ineffable.
The West, on the other hand, doesn’t seem to be in hot water on this score. For we can say that the difference between "being begotten" and "proceeding from" is that being begotten is from one necessary causal relation whereas proceeding is two necessary causal relations (since of course the Spirit presumably comes from the Father and the Son).
P1: All Three members of the trinity are necessarily and essentially (N+E) distinguishable in every possible world.
P2: There is a possible world W* were God did not create.
P3: In W* the persons of the trinity can be distinguished by having different necessary and essential casual relations between each other.
P4: The traditional Trinitarian causal relations plus the insertion of the Filioque explains the N+E distinctions between the members in a possible world W*
C: Hence, the Flilique is more reasonable than not.
Thus if one wants to have more explanatory power in their Trinitarian theology and philosophy, they ought to adopt the western view of the Trinity (namely, the filioque).
