Being able to survive in a vacuum has nothing to do with strength...bacteria can exist in the vacuum of space, and we
know they aren't physically strong.
As for strength comparison...who really knows? We have never seen the "full" extent of any xenomorph's strength on a comparable level to another one within a different film. They're effectively the same creature, they've been tweaked and adjusted from film to film, and their physical strength varies as much as the script wants them to.
The xenomorph in the first film was a drone, and hadn't been around for very long. The warrior in Aliens was alive for a considerably longer period of time. On a level of physical maturity, the warrior is naturally the stronger, without a doubt.