Just wanted to throw out a quick opinion – hopefully I will get the chance to add to this post tomorrow…
The RC position of making the teachings of the Church and the decisions of the Councils the standard by which truth is weighed and determined over and against Sola Scriptura only ends up handicapping, nay, emasculating any actual apologetics effort in areas of doctrine such as the Trinity or the Vicarious Atonement.
I for one would agree with a Roman Catholic that part of the evidence for the Trinity is that it has been taught by the Church Universal since of old time and other alternatives condemned as heresies. However, in an actual debate with a Unitarian who knows their stuff, the Infallible Magisterium does more to undermine the orthodox position than to defend it.
As Martin Luther pointed out, a doctrine must be defended from plain reason based on the Holy Scriptures; otherwise it is at best opinion, or at worst blasphemy.
This is why a Roman Catholic will never win a debate with Anthony Buzzard, because most often they major in Church politics and minor in actual Biblical texts.