The not-so-perfect organism

You are right, the xenomorph's reproduction is more complicated and could be more vulnerable than the neomorph. 

But about hé spores... It's a haploid type reproductive system, which means, it can't adopt itself well, if the environment changes because of some reason. So at this point it's more vulnerable than the Ovomorph. If it's a spore and só it's haploid, the neomorph products that small kind of mushrooms (??? in the picture you linked) itself, there's no queen etc.

The xenomorph should be diploid, especially if it based on human reproductive system. So it can react to the environmental changes better. But of course, I don't know any details about their biology, I'm just guessing.

Answering to your thoughts... As you mentioned above: maybe the xeno isn't that perfect ín the "childhood", but in the end it's stronger than the neomorph. The facehugger can attack just special species, this ensure it's development. 

Working out through more science, biology, and related sciences-stuff than I really want to think about allowed me to come pretty close to an Organism in which 'It's structural perfection is matched only by it's hostility'.

Or 'The Perfect Organism' insofar as such a thing can exist in our universe.

ALIEN: Manticore will re-introduce you all to The Alien (not some knock-off 'xenomorph' bastardized droid-experiment) That's why I've been so scarce around here of late, I spend much of my day working on my books, and just because ALIEN: Manticore is fan-fiction does not mean I treat it as less-important, nor do I give it any less effort.

I am really looking forward to introducing you all to what I hope is everything Giger and R. Scott could want from their creation in it's being and biology.

@ esther85

You're right, the ovomorph does provide a lot more protection than the spores do. And yes, while the spores could potentially infect any species, that does make it prone to genetic inferiority, while the facehugger only being able to infect certain kinds of species gives the Xeno it's genetic "purity" as Ash said himself. You have some very good points there.

The Xenomorph is perfect once it reached maturity. It is vulnerable in earlier stages, yes. But it also has the element of surprise. You gotta consider that rarely anyone ever encountered as many Xenos as Ripley and survived even one encounter.

So whoever encounters an Ovomorph, a Facehugger or even a Chestburster won't even know what he just saw, giving the Xenomorph time to develop.

Now that we definetely know that the Xeno has no need to breathe or eat, we can perfectly assume that it is perfect. Atleast in space.

@ Benni_RoR

Yes, it is truly a Star Beast.

When David confided to Walter that he had created the perfect organism, he was talking about the Xeno that had recently burst out of Captain Oram. He wasn't talking about the Neomorph.

If the Xenomorph and Neomorph were introduced into an ecosystem and left to do their thing (without human intervention) what you find would happen is called Trophic Cascading. The Neomorph is a classic r-strategist. It would rip through the indigenous species and establish itself. However it is a meso-predator, if left unchecked it would annihilate the biodiversity of the ecosystem and eventually exhaust all resources and die off. The Xenomorph is an Apex predator. It's role is to keep the meso-predator population in check and maintain a stable Carrying Capacity of the ecosystem.

Both species are "perfect" in the sense of the archetypical roles in ecology

@IRaptus: Where is your evidence that the Xenomorph would keep the meso-predator population in check?

Nathan Adler no proof brother. I was trying to apply what I know and understand about Ecology (a personal interest) to an alien environment with alien species. Just my brain trying to slot our beasties into established patterns in nature.....it doesn't work neatly lol.   

That being said, in all likelihood both species are so hyper-aggressive they would likely directly and indirectly destroy all life very quickly, including themselves. 

I think Ash was trying to scare the remaining survivors into believing their fate was sealed.  I think he knew it could be destroyed.  In Aliens, we knew fire could hold them back and he just suggested fire as a possible option in Alien.