Apologies beforehand, since I’m no expert on Protestant doctrine and know even less of Catholicism. But the issue I’m addressing is this: Is a system of greater individual choice in determining right theology to be preferred over one with more institutional authority?
One can answer this question (1) just in terms of which approach is more likely to yield right answers, but we might also consider (2) whether it is also important how the truth is found and, finally, (3) what is done with the truth after it is found.
Re (1): My tentative answer is that it is best to have both in place, just as (providentially?) we do. That is, there are obvious strengths and weaknesses with each, but we can eat our cake and have it, too, if there is an institutional church (Catholicism) at the same time as individuals (Protestants) are constantly rethinking things. There would be, ideally, respectful discussion between the two, even as there is some inevitable tension between them. An established church is less likely to go off the deep end, but any bureaucracy can drift and needs external checks. In any other discipline, individual research and questioning is embraced, and at the same time we know that only a foolish individual ignores the canonical work of those who have gone before him.
Re (2): There is value in encouraging people to search for the truth. And the most relevant truth may be different for different people. (I hasten to add that I’m not saying that there is no absolute truth; I’m just saying that, for example, person A may be most moved by one part of the Bible and person B by another part.) But I should add that Catholics as well as Protestants can be searchers and that there are indeed existentialist Christians of both stripes (see Walker Percy and Soren Kierkegaard).
Re (3): Perhaps the truth is more likely to be lived if the individual has had to do some digging (in himself or elsewhere) to find it; on the other hand, depending on how much an individual trusts himself versus some other relevant authority, it may or may not mean that the individual will take a truth he has discovered more seriously or is more likely to discard it.