It feels that the Neomorph is way more of a “perfect organism” than the xenomorph. First off, the life cycle is more efficient. Nothing is quicker than spreading disease than an airborne pathogen.
It depends on what is the measure of better.
* For wiping out animal life on a planet, the Neomorph is the better creature.
- Black goo infected spores would quickly spread through the air around a planet creating fungus (that produce more spores).
The fungus waits for a victim.
Eventually the Neomorphs/fungus will have done its job. All animal life is infected and eliminated. Then the Neomorphs/fungus will eventually die over time and with no way to get off the planet, their spread ends.
It seems that if anything, an Egg and a face-hugger just complicate things.
It is the difference between the more random reproduction of the Neomorph and more deliberate choices which are possible with the Xenomorph.
- The Xenomorph species has a Queen who can choose the most protected place to lay eggs, like near a nuclear reactor ("Aliens") to protect it from human attack.
- The Queen/Xenos/Facehuggers can stow away on a ship and strategically hide, place eggs on ships.
The Xenomorphs can then spread through the galaxy as stowaways.
So, the Xenomorphs are taken to other planets and can reach other ships.
* That's the main advantage of the Xenomorph.
The Neomorph needs someone (usually the Engineers) to place the black goo in the air on a planet to infect spores. Then the Neomorphs stay on that planet.
The Xenomorphs will roam the galaxy.
PS. I'll add a very speculative film theory just for fun. I'm not trying to prove this is true.
Could the Xenomorph place eggs in locations which may increase the chance of reproducing with certain creatures over others?
In "Alien 3" the viewer learns that a Xenomorph chestburster could come out of a dog.
Doing some wild retconning of the "Alien" Director's Cut (where the Xeno can transform humans into eggs), could the cat (Jonesey) have been transformed?
(When I first saw "Alien", I wondered if Jonesey had been infected in some way by the creature.)
- Anyway, could Xenomorphs make choices about what creature to breed with in picking out better mates?