One of the greatest differences:
On Chapter 9, when you put both safe dials in. The dials start turning on their own, and the face on the painting explodes. (It explodes on the other difficulties, but the dials don't usually start turning on their own)
I'm not kidding, that literally made the entire play through worth it, it scared the $^#&@! out of me lol.
Thought it was funny that nothing throughout the 45 hours I have spent on this game scared me. And I played on casual, and got the crap scared out of me because of such a minor difference.
I was wondering if there are any other known differences between casual and the other difficulties in terms of puzzles?