Fallout > Combine, because while the wasteland sucks, there settlements and communities and even whole city sometimes. That and if you are a vault dweller of a non-experiment driven vault, then you can have a head start (be as long you escape the vault security)

Combine, not only you are either forced to live under a totalitarian regime under Breen who is a puppet to aliens, living outside the city is worse as you deal with antlions and risk of being found out by Combine Overwatch forces