MacCulloch's work is more comprehensive. He has no axe to grind. He begins with a survey of the Western Church on the eve of the Reformation, exploring all the common assumptions of the time -- as well as the obvious needs for renewal that everybody was talking about.
He gives a lot of attention to sweeping reviews of what was going on all over. Instead of merely zeroing in on the drama of events in Germany, or England, or Geneva, he examines scores of minor characters, many of whom were related to events in ambiguous fashion.
What I'm learning from this is that there were a LOT of people who were caught up in the sound and the fury, and who for the longest time could have gone either way. Right up until the end of the Council of Trent, there were Roman Catholic bishops and cardinals who were experimenting with Protestant-style reforms. Right up until the split was made permanent, there were political leaders and theologians all up and down the spectrum and in every country of Europe trying to find a way to re-unite the Church. Guys like Luther and Calvin and the Popes were irreconcilable, of course -- but many of their followers were not.
So what happened? Ultimately, the Church -- and Europe -- divided, more or less permanently. Faced with ambiguous and tantalizing ideas, Protestants opted for certainty. There just had to be a Single, Right Answer for every Question -- whether it was the mystery of election or the mystery of the eucharist. As each wing of Protestantism staked out what they felt was the Single, Right Answer to each question, all other possible answers or influences were ruled out. This is why the various Protestantisms could never agree among themselves, I think. Each had seized upon a set of Answers which was less than the whole of the mystery, but having seized upon those Answers, they had to rule other Answers out entirely, since you couldn't have two Right Answers to the same Question.
In doing this, Protestants as a whole moved away from the Center they had been trying to grasp. In order to achieve clarity, they sacrificed ambiguity. But the Catholics did no better. MacCulloch details how the Popes presiding over the long-running Council of Trent used it to defeat Conciliarism at last, seize official control of everything, and even define their beliefs as over against Protestantism: in effect, the Roman Catholic Church opted for less than the Whole Truth in order to establish a brand that would be distinct from their polemical foes' brand. So the Roman Catholic Church also moved away from the Center.
Catholics today look at their own Church as the center about whom the fragments orbit. But I say, the RCC is itself a mere fragment of what once was, though perhaps the largest remaining piece. And all the fragments of Western Christianity now revolve around, not each other, but a common center of gravity somewhere off-center to all of them. This leads me to wonder about the earlier split between the Catholic and Orthodox wings of the Church: could we not say the same thing happened there?
All of which means that the entire visible Church -- Catholic, Protestant, Orthodox, Coptic, what-have-you -- is rotating on an axis that is not at the center of any of them. Christian re-union -- real unity, not just merger of organizations or absorption of one by another -- would require us to find and grasp once again that center, where Christ is. It would require all of us to move away from the positions we have staked out for ourselves and toward that center.
This is what is so terribly wrong with ecumenism as we find it being practiced. Catholics talk about ecumenism, but in the end all they say is "admit you're wrong and join us." But "you" are not what "we" once were. "You" are as broken as any of us. The object should be for all of us to become what we should be. Meanwhile, Protestants talk about ecumenism, but in the end, many of them think they can compromise their way to unity. But the answer isn't in being LESS than each of us was before, but in all of us becoming MORE what we always were trying to be. And the Orthodox play cagey as always.