There is the final distinction... authority. To whom has it been given and how do we know? It was given to the Apostles by Christ and we can see it in the New Testament as they wielded it. They were not commanded by Christ to write a book so the faithful would have something to follow (and be patient for Guttenberg to come along 1,500 years later so everyone can finally have one). They were commanded to grow Christ's Church and this Church has authority (1 Tim 3:15) as shown by the Epistles--letters written for reproof, correction, and encouragement.
We can see in the beginning of Acts that the Apostles had the authority to bestow Apostleship to replenish their numbers and they had the authority to define doctrine (Acts 15) binding on the whole Church. This is the basic nature of the Catholic Church you spurn and the authority it still bears.
And therein is where we will never agree. You believe in extra-Biblical/extra-Scriptural authority. I take Galations 1:8 quite seriously. Anything being added to the Gospel, any other doctrine or extra-Biblical claim to authority is anathema. Adding to God’s already sufficient work through his Son is preaching another Gospel. In no way does the vatican possess any Biblical authority.