Militantsparrow, may I assume that though you have identified yourself as Catholic, you have, in fact, intellectually stepped away from the Catholic Church and are investigating the respective claims of Catholicism and Orthodoxy with the intention of committing yourself to whichever Church is able to provide the most rationally compelling arguments and evidence? I understand this process, but I have to wonder if it in fact is the right way to go about things.
For example, you and your Orthodox dialogue partners are arguing about historical "facts," as if historical research alone could prove or disprove the claims of either Catholicism or Orthodoxy. Neither committed Catholics nor committed Orthodox read history in a "neutral" fashion. For both the reading of history is informed by belief and dogma. John Henry Newman explains:
Why should Ecclesiastical History, any more than the text of Scripture, contain in it “the whole counsel of God”? Why should private judgment be unlawful in interpreting Scripture against the voice of authority, and yet be lawful in the interpretation of history? … For myself, I would simply confess that no doctrine of the Church can be rigorously proved by historical evidence: but at the same time that no doctrine can be simply disproved by it. Historical evidence reaches a certain way, more or less, towards a proof of the Catholic doctrines; often nearly the whole way; sometimes it goes only as far as to point in their direction; sometimes there is only an absence of evidence for a conclusion contrary to them; nay, sometimes there is an apparent leaning of the evidence to a contrary conclusion, which has to be explained;—in all cases there is a margin left for the exercise of faith in the word of the Church. He who believes the dogmas of the Church only because he has reasoned them out of History, is scarcely a Catholic. It is the Church’s dogmatic use of History in which the Catholic believes; and she uses other informants also, Scripture, tradition, the ecclesiastical sense or phronema, and a subtle ratiocinative power, which in its origin is a divine gift. There is nothing of bondage or “renunciation of mental freedom” in this view, any more than in the converts of the Apostles believing what the Apostles might preach to them or teach them out of Scripture. (Letter to the Duke of Norfolk)
Newman's argument obtains whether one is Catholic or Orthodox. Why? Because faith in the Church is as mysterious and supernatural as faith in Jesus Christ. Does anyone truly believe that Jesus is risen because he has determined that a divine and supernatural act is the most probable explanation for the historical evidence? Of course not. If he did, his faith would be a flimsy reed indeed, just waiting to be crushed by the latest historian who claims he can prove that Jesus never existed or that his bones were stolen by the disciples.
Newman dismissed the idea that faith in the Catholic Church was contingent upon proving the supremacy of the Pope. He believed this was the wrong way to about things. Newman did not come to believe in the claims of the Catholic Church because of the Pope. He believed in the Pope because he first believed in the Catholic Church. Newman came to believe in the claims of the Catholic Church because he became convinced that the notes of apostolicity, catholicity, unity, and sanctity were fully embodied in the Catholic Church. “To the poor is the Gospel preached,” Newman wrote. “Accordingly the notes of the Church are simple and easy, and obvious to all capacities. Let a poor man look at the Church of Rome, and he will see that it has that which no other Church has.” Newman was insistent that the infallibility of the Pope is not the basis of the Catholic religion. Catholic apologists need to learn from Newman on this point. I suggest that one can mount a similar argument on behalf of the Eastern Orthodox Churches.
I do think it is possible to read history "critically." This critical approach requires one to bracket, as if were, one's dogmatic commitments and to weigh the evidence according to the criteria of secular historical science. I believe it is helpful and necessary to listen to the judgments of "neutral" historians. When one does, one discovers that the testimony of history is anything but obvious on the questions being discussed in this thread. But the simple fact is, you aren't going to find critical historians on an internet forum like this. History as presented by apologists is anything but neutral.
Which is more reasonable, Catholicism or Orthodoxy? It all depends on where one stands. The committed Catholic will always find his religion to be eminently reasonable; ditto for the committed Orthodox. So how does one negotiate their competing claims? By all means continue to read, continue to assess the evidence and arguments; but ultimately, I think one simply needs to experience the faith as it is lived in each Church and see for oneself. If one is concerned to discern which Church is truly apostolic and catholic, then perhaps Newman's counsel is apt: Which Church would St Ambrose or St Athanasius recognize as the Church if he were to walk into a Catholic or Orthodox parish today? In which Church are the notes of the Church most fully embodied and lived?