In the comments on a post below, the discussion turned to the question, Whether it is harder for "cultural Christians" to become "true Christians" than for atheists to become "true Christians"?
Setting aside the question of defining and distinguishing "cultural Christian" and "true Christian,"* the basic idea of the Yea side is that those who are born and raised in a Christian culture tend to settle into a little well of complacency, so to speak, from which they are not easily roused. Atheists (or non-Christians in general), being less accustomed to hearing [what they are told is] the Gospel message, much less hearing they are good Christians, have a greater potential to accept Christ's call in their lives.
My take on the question is that we say which transition is easier, not only because we don't actually know, but because it's an ill-posed question to begin with. How "hard" it is for someone to become a true disciple of Christ is not determined by whether he is a cultural Christian or an atheist, and in fact the very difficulty of becoming a disciple -- an act which is, after all, utterly dependent on God's grace -- is not something that admits of being measured at all, much less between people.
The question begins by assuming a too-simple state flow:
But these are hardly the only possibilities. An atheist who becomes a Christian does not necessarily become a true Christian; giving oneself over to Christ is a process, often a long slog for the best among us. The just man falls seven times a day, and so forth. We can immediately explode the state transitions, and still not claim to have covered everything:
Does it make sense to rank these transitions categorically, according to difficulty?
If you think it does, and if you're inclined to try, then you should be sure to compare things that are comparable. For example, I don't think it's right simply to compare those atheists who became true Christians with those cultural Christians who did not, i.e., the red portion of this diagram with the green portion:
This sort of comparison neglects, not just the cultural Christians who become true Christians, but all the atheists who don't become any kind of Christian. A fairer comparison, I think, would look like this:
That is to say, don't ask what a cultural Christian would have to do to become a true Christian, ask what a former cultural Christian did have to do. And similarly with a former atheist. Otherwise, it becomes an exercise of listing the factors that keep cultural Christians complacent without listing the factors that keep atheists atheistic.
Again, though, I'm not sure it's a sensible question to begin with. And whatever else, we shouldn't lose sight of the central role of God's merciful grace in all of this.
*. For the most part, this discussion can be rephrased in terms of "cradle Catholics," "adult converts," and "Catholic disciples of Christ," with what I'll assume are obvious enough changes to not need specifying.