I've switched around between the three settings to get an idea of how they balanced it out. Correct me if I'm wrong here but it seems to me that enemy HP and AI is identical across all difficulties. Audio and visual range might change? Difficulty appears to mostly relate to the availability of items. Difficulty of the stealth sections, so far, is identical for me. Clickers still 1-hit on easy same as they do on hard.
I'll continue through on hard for no other reason than it makes no difference to my play style, might as well get the trophy.