Drengin: The Slave hubs are basicly the best (colony-unique) thing you can place on a tile in the game. Adjacencies properties are insane. The Approval bonus from the manufacturing buildings is nice, too. They also have stronger approval buildings, which compensate for the higher foodcap through their slave- and food-hubs (gets +% food adjacency instead of +% growth).
Altarian: The social matrix is a nice combined research/manufacturing hub. Their approval buildings are slightly better I think. The downside is they ahve a terraforming improvement less. The have a 10% jamming tech.
Iridium: combined influence/wealth buildings.
Krynn: combined approval/influence buildings primarily.
Yor: Tech tree for the synthetics trait, which focusses on building instead of breeding population. Lacks manufacturing and research capitals, which hurts.
Iconian: Strong Ship improvement techs. Unique hub gives a slight boost to food. They also have a special research building.
Thalan: Hive tech is amazing. Especially after base colony production nerf. Hyperion matrix is an amazing research unique and directly and conveniently leads to deeper knowledge. Also has useful fleet boosters like jamming and additional hull capacity boosts.
Torian: Strong Ship improvement techs (20% jamming and 20% damage reduction). Have slightly better food buildings and approval buildings with better adjacency (gives to everything). A downside is there different tech building tree, which lacks hubs and the research capital. Life support takes more space, but provides higher reach.
Arcean: Can build manufacturing and research galaxy uniques in the age of war, long before any other faction. Movement boosters and a semi-unique ship repair tree.
Snathi: Hub buildings from Iconians, Drengin and Altarian (very strong), techs boost the chances of conquering enemy ships after battle, super-cute leader 3d model. BUT: Can't upgrade growth improvements and totally lacks counters to jamming.
There is some more minor stuff about techs being accesible in the first age, but the above are the most important points I think.