They focus on arguments about Mary, purgatory, Saints, councils, Papal authority, and traditions. That’s not to imply that differing views on these subjects aren’t vitally important because they are. But they all generally point to the spiritual elephant in the room of every Catholic and Protestant; It’s the subject of salvation and how to obtain it.
Witnessing
The question that needs to be addressed in light of scripture and in view of eternity is: Should Protestants evangelize Roman Catholics?