I guess I can relate back to the discussion I had concerning the different styles of INFJs and INTJs. INFJs focus more on 'values' while INTJs focus more on 'facts'.
That's probably the best way to discern the main difference between the head and the heart. Both can challenge many established notions and the status quo, but from different angles.
Take UFOs for example: a "Thinker" may critique belief of UFOs based upon actual scientific data and logical improbability. If a "Feeler" were going to do the same thing, it'd probably be more along the lines of Benjamin D. Wiker's critique where he addresses the flawed philosophical assumptions(ie 'values') upon such a belief is based upon.
Here's a good example of what I'm talking about:
Wiker does appeal to scientific data and improbability to back up his arguments, but his argument is primarily about flawed 'values' that lead some to believe in UFOs rather than flawed 'facts' or data so to speak(you get the idea)."Christians should be equally wary of the idea that God would somehow be a second-rate deity if He allowed human beings to be the only intelligent embodied beings in the universe, since that would mean a lot of wasted space. What frightens us into making such claims is, I believe, the immensity of space itself. But while the vastness of the universe rightly humbles us, its size means nothing to God, an immaterial intelligence. Since He has no size, it is all the same to Him whether He makes the universe as big as a pin or a pin as big as the universe."
So both the Head and the Heart provide firm basis for "free-thinking". One is not necessarily more "free-thinking" than the other. They just operate on different playing fields.