What determines system space loot/broken ship level/rarity?

[inaliFTW]

I've been traveling around looking for the best ships to repair in space. I go to a 5 technology system and find low level ships. I go to some with higher danger/darkness, sometimes I find higher level hips, sometimes not. Is is a combination of all the system factors(danger/darkness.tech)? Is it random? Or is it individual? Just trying to figure out the system thanks.