If you had to chose, which situation would you rather be in?

I think I'd pick Aliens. The only thing I would need would be some up to date, accurate blue prints and lay outs that are pretty easy to understand. After all you don't want a xeno dropping in on you and buggering up the ceiling. It does help if you know were things are. Like toilets, which is possibly why certain details get overlooked especially if your in new surroundings in need of a dump. You'd think that after a large hypersleep that would be first thing on the agenda.

just get in the air vents with another person and go legs to legs and start fireing

For me it would have to be Aliens. For no other reason than I'd get fire a pulse rifle and smart gun