What are the main differences between the practice of Christianity as a Protestant and as a Catholic?
I can answer that in a heart-beat: the Mass. Protestants can go to church on Sunday and sing very stirring hymns and listen to compelling and moving sermons. They can even have great fellowship. But that is all.
In many places Catholics can have good music and good preaching and fellowship as well. But Catholics can also go to church on Sunday and the music can be dead and poorly done and the preaching can be sterile.
Nevertheless, they behold the actual Body and Blood of Jesus Christ offered on the altar in a way that transcends time. What happened on Calvary is brought into their lives in a concrete way through the Eucharist. Then they partake of it—not as a symbol, but as He gave it to His apostles in the upper room. Through their successors, His bishops and priests, He has been giving it to His people ever since. Nothing that happens of the face of the earth can equal this miraculous expression of His love. THIS is the main difference.
Fr. Vincent Serpa, O.P.