Habitats, and why do you use them? (Or don't)

[GAGA Extrem]

Habitats are fantastic for tall play.

(1) Extra living space for relatively low cost (with alloy upkeep being less dramatic after the alloy production buffs).
(2) They provide extra pop growth, which is always welcome to compete with bigger empires.
(3) They provide a lot of building slots per admin capacity.
(4) Main colony building can be upgraded at low pop count, allowing early use of advanced buildings.
(5) Tend to have very high stability, which makes them great for refining.
(6) Can be used as super-heavy FTL inhibitors, arguably better than Citadels at that job during late game.
(7) Great at providing extra NF capacity while self-sustained (in terms of E & CG).

 

[GAGA Extrem]

[...]
5: I don't understand? Why is stability important? Unless you're running a billion slaves.
6: True again, but at that point people tend to have jump drives. And the Awakened Ascendantries have tons of soldiers.
[...]

High stability increases job (and TV) output, up to +30% at 100% stab.

Forcing an enemy to use their jump drive to advance grants a pretty decent opportunity to counter-attack. Forcing them to bring transports along adds an extra achilles heel to their forces, particularly for human opponents.

If we talk about competetive MP (which was not part of the opening post), I'd imagine the only thing that matters is which ME can faceroll their neighbors first within the first 20-30 years.

[...]
(1) When you have extra 3k to spare, it is significantly cheaper to just conquer new planets. So this holds true only if you restrict yourself as tall/pacifist playstyle. [...]

If you are fighting a war were you are not just facerolling your enemy, chances are that you will suffer significant fleet losses to (ideally) make gains. It is not unreasonable to end up in a situation where investing alloys into a habitat over an extra pair of battleships is the better choice - especially when the Habitat can increase your alloy output in the near future via extra slots for alloy factories.