So considering how fun it is, how good it is, how good their perks are what killer is a better choice, Demogorgon or Xenomorph?
I'd say you get more out of Xeno in terms of power & perk value than you do with Demo.
While demo's shred attack has faster activation timing and feels easier to use, Xeno's tail attack can be even more deadly and probably has a higher skill ceiling. Turrets can sometimes be annoying, however most of the time they're pretty easy to deal with and their effects can just be negated by getting in a tunnel and quickly recover should they kick you out of Crawler Mode.
Also Xeno gets more value out of it's tunnels than Demo does with it's portals.
I think Xeno is just better in perks and Gameplay.