Horatio=The ability to settle anywhere and genemod various pops into more Horatio (With various bonuses. Though it costs extra food.)
UE=Industrial bonuses out the Wazoo and the ability to get a massive amount of influence and use it for buyout. 

Lumeris=Prepare to make a LOT of Dust. You also can technically build outposts anywhere in your line of sight. Then sell the outpost to another faction if you want.
Sophons=All about Science. You know what tech's other factions have parsed out and you get a bonus to research speed for being the first one to discover a new tech.
Vodyani=Extremely mobile faction, you don't colonize systems directly and instead you require Arks to settle a system. You build more population by essentially sucking the lifeforce out of other populations.

The Vodyani also have this cool effect where when you're playing human opponents, they whine about how OP the Arks are in combat, while secretly wishing their faction was half as cool as the Vodyani.

Ikeaboy33 wrote:
is it possible to play tall with some faction, like having 2-3 systems, and still maximising your faction in a competetive mp game

The Automatons?

But they're not in this game...