Catholics and Protestants: The Fundamental Difference
This was a reply to a comment on the post below, but it's kind of lengthy, so I'm posting it here. I'm also going to cross-post it over at X-Catholics.
As it so happens, I'm currently composing a post on why I became Catholic in response to many requests. You ask "Could you elucidate why you left protestantism and turned to catholicism?"
As a philosopher I first have to give the obvious answer: because I think the Claims of the Catholic Church regarding her authority are true and incompatible with Protestantism. Note that I designate a sub-class of claims of the Catholic Church, namely those regarding the Church's authority. Most claims of the Church are perfectly compatible with Protestantism (well, with magisterial Protestantism anyway, part of the problem is that there are like 30,000 (literally) different protestant denominations (if you count all the independent ones separately) so making claims about what "Protestants" believe can be tricky: most Catholic doctrine is compatible with Lutheran, Presbyterian, Anglican, and Evangelical beliefs).
What Mother Kirk claims is that she is the fullest expression of the visible Church on Earth and that the Bishop of Rome is the final authority in matters of the Faith and governance of the Church. The basis for this claim is the doctrine of Apostolic Succession. I've got a brief summary of some evidence for this doctrine here, and am working on a draft of a fuller argument. So the basic claims of the Church are as follows:
1. Jesus was the Jewish Messiah, promised in the Old Testament, and expanding his plan to we Gentiles.
2. Jesus founded a visible Church to carry on his teachings and selected the Apostles to govern this body.
3. Peter was the Chief of the Apostles as witnessed by Peter's divine anointing and unique reception of the Keys of the Kingdom (Matt 16) which represent the vice-regent of the King, his special relationship with Jesus ("feed my sheep," Gospel of John, Chatper 21), and his authoritative pronouncement at the Council of Jerusalem (Acts 15).
4. The Apostles anointed new leaders--called Bishops (episkopos in the Greek New Testament)--and when an Apostle died, someone took their place (just like occurred with the loss of Judas at the beginning of The Acts of the Apostles in the New Testament).
5. The line of Apostolic Succession has never been broken.
The doctrine of Salvation among Catholics and Mainline and (many or most) Evangelical Protestants are essentially the same (no more differences than among some Protestants): we are given the Gift of Faith to trust in the finished work of Christ in atonement for our sins. The rest is details.
As a Protestant I already accepted #1 of course, but gradually came to believe the rest of them as well. There's much, much more to the story, but a sufficient condition for my becoming Catholic was being rationally persuaded of #'s 2-5 (in addition to #1).
This is just the bare bones and only states the minimum sufficient condition, so stay tuned for a more robust answer. Hope that helps.