Greetings. Perhaps the best I could do would be to give a brief overview of how I myself came to be Orthodox Church, that way I can hopefully avoid being polemical. Even while still a Protestant I became convinced that our Lord founded a specific Church. There is Matt. 16:18-19 of course, but I think many verses are very difficul to handle outside of that perspective. Why does Hebrews say to submit to those over us, for example, and who decides who those men who are over us are? (Heb. 13:17) Paul says in one letter that he left Timothy to appoint others, but does that mean that you have to have a special appointment to appoint others? And if so, who was the original ones that did the original appointings, and how do we know that the people appointed are to be trusted?
Coming upon Matt. 23 and paying attention to it for the first time was a real thunderbolt for me. Jesus had blasted the pharisees elsewhere, and now here he was saying "whatsoever they bid you observe, that observe and do" (Matt. 23:3), though of course he said not to do as they did. So was the existing authority so important that people should listen to their teachings, even when they were hypocrites? And after the Church started, did the concept of authority just drop out of sight and everyone started doing their own thing? There seemed to be some passages to support that, but what did the bulk of the Scripture say?
People kept telling me to research what the "Church Fathers" said, so eventually I did wonder, what did the early Church say? What did those writing in the 1st century and 2nd century say? Clement, Didache, Melito, Ignatius, Ireneaus, Justin Martyr, etc. What I saw was a Church that was connected by it's faith, hierarchy, practices, and observance of certain continual celebrations (e.g., eucharist). Eventually I became convinced that yes, there was a Church established by Christ, spread by the apostles, and continued throughout early christian history.
The question then became, was it "corrupted"? Did Constantine's toleration or Theodosius' making it official, for example, lead it astray? Regarding that, since there were a lot of doctrines not really talked about in the early church literature, I tried to work in reverse chronological order. I started with what the doctrine was today, and worked my way backwards trying to figure out where or when it came into being, or at least when it started to really get talked about a lot.
An overarching principle that I held to, though, was that I realized that probably not everything would be resolved or detailed to my full intellectual satisfaction (I hate saying that! it sounds so arrogant, but I think you know what I mean). I allowed that, if the Church was a "truth telling thing," if it was what it claimed to be (the body of Christ, headed by the Truth incarnate Himself), that I would trust the Church about the things I didn't understanding or just couldn't fully agree with. After all, if the Church really was led by the Christ, trusting what the Church taught over the years was essentially the same as trusting the Scripture, the Bible etc. Yes, there was the possibility for error, but I had faith that in the long run, properly understood, these things were protected from error.
And what does "the gates of hades" mean, anyway? Part of what the fathers saw in that term was heresy, schism, etc. In other words, things that corrupt church doctrine, cause division, etc. So for the the gates of hades to not prevail, this meant that their had to be some Church out there which had kept things faithfully, who had "held the traditions handed to them by word and epistle".
So the question after a bit of exploring became, Catholic or Orthodox? (I would now include Oriental Orthodox in that question, though I didn't at the time) What about papal supremacy, papal infallibility, the immaculate conception, purgatory, created grace, etc.? Or on the other side, what about Orthodoxy not having an ecumenical council for a long time, or their distinction between the essence and energy of God, etc.? Is Orthodoxy too mystical for it's own good? Is Catholicism too scholastic for it's own good? Is Orthodoxy stagnant? Is Catholicism innovative?
I'll admit that it was quite a struggle for a time. Eventually though, I became Orthodox. I think there are a lot of confusing issues, and many things are far from cut and dry. Purgatory, papal supremacy, etc. all seem to have patristic support--and I'd go a step further and say that yes, Fathers did affirm some of this stuff that the Orthodox don't affirm. But since I'm Orthodox, I'm sure you can guess what my final conclusion was on a lot of these issues.