I could be wrong about this, but from the EO posts I have read in here, I would say Protestants are more likely to reunite with the CC than are the EO. That would vary, of course.
I live in an area that is overwhelmingly Protestant, and in which there are no EOs or OOs. Every year, a good number of Protestants convert to Catholicism here. The only movement I see in the other direction is when somebody wants to divorce the wife of his youth and get another. The former far outnumber the latter.
I have, on occasion, handed a Protestant friend the Catechism of the Catholic Church and invited him/her to go through it and see how much of it/she disagrees with. There’s very little, really, and for good reason. Protestant beliefs and mores are largely taken from the background of western culture which, itself, was formed and directed by the Catholic Church. Protestant churches, for the most part, have almost no “doctrines” at all, and what most of them believe are simply the things they learn from the background with a kind of sectarian gloss over them. When the Pope speaks, and what he says is publicized, many, many Protestants listen. In talking to most (not all) Protestants about Catholicism, I find that they actually listen. The more they study about Catholicism, the less hostile they are to it, unless they have compromised or set their lives in such a way that they retain the hostility defensively.
Many EOs, on the other hand, (and I am sure this is not true of all, though it is certainly true of many who post in here) are hostile to the CC in an altogether different way. Many EOs regard the CC as “Protestant”, so to speak. Actually, worse than that. I daresay that if one of the EOs who regularly post in here went through a Catechism of the CC, they would underline more as objectionable than most Protestants would. That is because (and I only know about posters in here) some EOs regard every single thing the CC holds that postdates some council or other (Chalcedon, I think) as heretical, “new”; an “innovation”, illegitimate. Protestants are more inclined to simply see if what they read directly contradicts something they already believe, and do not automatically throw things out just because they were not the result of a pre-schism council. Protestants grant to the CC the right, nowadays, to be wherever it wants to be. The EO does not think the CC has any business being in Asia, Africa, the Middle East, Russia, Ukraine at all. Not at all. The EO does not consider it legitimate for the CC to proselytize worldwide; something few Protestants begrudge.
Perhaps I am biased in my belief that Protestants are much more likely to reunite with the CC, because I know a huge number of Protestants of many denominations very well, and know what they think, while my experience of EO is from a little reading and from this forum, which might be too narrow. Some “high church” Protestant denominations already consider themselves part of the CC, more or less, but with the difference that they have slightly different emphases on certain things. “Low church” folk like Evangelicals are usually looking for that “closer walk with Thee”, and once they are persuaded it really is in the Eucharist, the rest is not too hard.
I realize there are the Jack Chick Protestant nut-job sects. But on the whole, I would say that the Protestants I know, and the ones I run across in here are far more friendly disposed to the CC than are a good number of the EOs I have met in here. Now, maybe the ones I am talking about do not really represent the general view of EOs. Patriarch Bartholemew does not seem to share their views, and I have seen him sharply criticized by EOs in here because of it. I hope he represents most of Eastern Orthodoxy’s thinking in this regard, but I am tentatively unpersuaded that he does; particularly among the Russians, who constitute, at least in theory, the majority of the EOs.
Finally, (but returning somewhat to what I said above) there seem to be cultural differences that appear to mean a lot. They are very hard to describe, and I would have a hard time trying to define them in one of these posts. But that really doesn’t exist between Protestantism and Catholicism in as deep a way as it does between Catholicism and Orthodoxy.
I would like to see an EO refute my contention that Protestantism (by and large, not in detail) is closer to potential reunion with the CC than is Orthodoxy. I really would. But to refute me, one would first have to WANT to refute me, and I’m not sure that desire is there. Prove me wrong. I really do respect the apostolic nature of the EO churches, and I would like to think I am wrong.
