Sound travels downhill.
When I'm hiking down a trail I look both up and down, but I think I look down and out more than up. When choosing a site, personally I think the terrain would dictate whether I'd go up or down. So if your imagining a perfect 45 degree slope and the was just tall pine trees and you could see all the way down and all the way up the hill. I think I'd feel safer going far up hill. Smoke travels up, people are less likly to look up, yellow water goes down, it's easy for me to look down, if a squad of zombie, back woods, hillbilly, axe murderers attacks my camp I already have the high ground.