You know, I actually enjoyed easy and medium the most, probably because it feels more random with how and when the Alien hunts for you. It's actually more unpredictable on those levels, and as a result more tense, than on hard. You're also more susceptible to becoming a bit more reckless on easy and medium because it sometimes feels like he's not around, but it's then that he pops out of nowhere. Very thrilling.
I just wish we had the ability to customize difficulty so I could set the Alien with a much longer leash to make him less routine while also restricting supplies and fuel.