I'm reading a great book called Caught in the Pulpit. This book disccuses the research from Daniel Dennett an Linda LaScola on atheists/agnostics who used to be clergy. Its fascinating in its own right and replete with deconversion stories that I personally can't get enough of.
One aspect of the book I am enjoying is the discussion of liberal clergy or as you put it "sophisticated" Christians. Essentially, what happens is a clergy member will drift over time from a fundamentalist theological position toward a more liberal theological position for a variety of reasons. This liberal theological position can be expressed as:
There are other points but these are the big ones that I can recall.
My guess is that liberal or 'sophisticated' Christians are abandoning supernaturalism and biblical literalism while incorporating scientific facts into their theology so that they can remain Christian with less of the "baggage" that comes from a fundamentalist position.
For me, I'm sort of torn. I like religious people who move away from fundamentalist position to liberal positions that allow them to be more humane. BUT it can seem a bit dishonest at times. For instance, these 'sophisticated' Christians attempt to take a 1st - 2nd-century Bible and try to interpret it to reflect their 21st-century morality and ethics.
But check out my book recommendation! It tackles your question head on and give you much more to go on!
Edit: formatting and reworded sentences for clarity