I picked Spacer, which was a complete mistake.
There isn't near as much content taking place in space, most of the action is happening planet side. And for the content that is in space, you don't need the additional O2 because you're usually working your way through tight corridors, potentially with a shotgun. Meanwhile when you are on a planet you are often traveling large distances across empty landscapes, a situation where you could really use the additional O2 to speed things up.
Anyway, Spacer is terrible and I think Terra Firma is a much better option.