Actually, I just found this out:
If you want to see for yourself the different in-camera editing functions in action, shoot a RAW file, and then, from the playback menu, choose “RAW image processing”, select your image you just shot, and you can see and compare what all the different in-camera editing functions do. I just found that Faithful brightens the shadowy parts of a portrait I just shot a tad (I like it) whereas Neutral doesn’t do that.
–Logan