Glory to Humanity! 

 The UE is my favourite faction. It is by far the most flexible Faction. You can persue any strategy you want and do well at it; unlike most other factions who are limited in what victories they can persue(Try going conquest as Vodyani or supremacy as Unfallen, it won't be a fun time).

 They also have the best faction quest in the game not only because of the afore mentioned flexiblity but also because you don't have to go too far out of your way to complete it unlike others(Vodyani I am looking at you). Their faction quest also has a signifigant impact on how you play the game and isn't just minor rewards like some other faction quest(Vodyani I am still looking at you). The story is also decent with Zelevas trying to find the traitor while also having fears and doubts over the matter of succession, that potentially leads him to fundamentally changing nature of the Empire, unlike other faction quest where nothing happens(Vodyani again! Seriously! The Vodyani would probably be my favourite faction if their quest wasn't the worst in the game).

Galathad wrote:

Glory to Humanity! 

 The UE is my favourite faction. It is by far the most flexible Faction. You can persue any strategy you want and do well at it; unlike most other factions who are limited in what victories they can persue(Try going conquest as Vodyani or supremacy as Unfallen, it won't be a fun time).

 They also have the best faction quest in the game not only because of the afore mentioned flexiblity but also because you don't have to go too far out of your way to complete it unlike others(Vodyani I am looking at you). Their faction quest also has a signifigant impact on how you play the game and isn't just minor rewards like some other faction quest(Vodyani I am still looking at you). The story is also decent with Zelevas trying to find the traitor while also having fears and doubts over the matter of succession, that potentially leads him to fundamentally changing nature of the Empire, unlike other faction quest where nothing happens(Vodyani again! Seriously! The Vodyani would probably be my favourite faction if their quest wasn't the worst in the game).

The UE are awesome. One of my tops.  I SUCK at cravers apparently.  Currently though my two favorite are the Unfallen, and the Sophons. Neither of the two are apparently favorites to others. I prefer a more turtle game play, when I want to just destroy everyone I definitly do the UE.

UE is so versatile you can't dislike them.  They can go pacifist, conversion, military, wonder, you name it.  Emperor's Will is amazing, end of discussion.

Horatio...well they're Horatio.  They have this ideal of such a complete victory over the galaxy.  They don't just want to win; they want to make everything Horatio, purge everything else, and make the galaxy perfect.  It's deliciously mad and that's how it feels to play them.

Lumeris, mixing business with pleasure.

Probably Unfallen or Horatio. They feel most relaxing out of all.

Daynen wrote:

It's deliciously mad and that's how it feels to play them.

I like the sound of that. Well said, sir!

Poor cravers and sophons

I would say Vaulters... was my favourite on Endless Legend so I am sticking with them now as well. :-)

Cheers

UE. While not that exciting mechanically, I simply find their story missions most interesting and immersive. Picking your heir, and later your whole focus, really feels like shaping the future of your faction instead of getting a minor bonus. And don't we all want to be the paranoid but charismatic leader that thinks of themselves as benevolent? :-D 

Lumeris might be my favourite if their central mechanic (dust, trade routes, buyouts) was not so completely broken by inflation on higher difficulty levels.

I would say Vodyani, because i have hope in Isyander one day leading them to greatness :D

I play Sophons quite often... guess I'm in the minority then.

My favourite faction has to be the Unfallen.

Unfallen, love their aesthetic and game style. It really feels like you're a tree spreading your roots slowly but surely across the galaxy.

favorite factions almost in this thread are humans and "robots" I find funny that there are a lot of hate in this forum regarding these types of factions xD I myself voted for Vaulters and UE and wouldn't mind having more Humanoid factions because I love them but I would prefer a robot factions after Umbral Choir, I would play Riftborn a lot if wasn't because I don't like the population mechanic xD but as a faction I like them. 

Horatio. Because:

1. their gameplay is unique. In every other 4x, there is always a civ with better production, better military, better research, etc. But none of them have the gameplay of chasing after and splicing the other races up.
2. I always make it a challenge to see how many races I can splice in a game. So, each of the Horatio game is always unique for me.
3. Their storyline is good. We are Horatio. Bow before the greatest beauty of the galaxy.

HISSHO OR RITO!

In all seriousness though, the Hissho are my new favorite. I truly enjoy playing them.
The Lumeris are my second favorite, because Dust Mafia.