I like the Lumeris the most. IRL I'm a sucker for pacifism and trade and such, so I can kind of identify with the Lumeris from a lore perspective. 

In game mechanics terms, they start on a temperate + fertile planet so early public private partnerships and Xenolinguistics give me busted amounts of science and industry. They start with two scouts, each with 3 probes, so exploration is a cinch. Micromanaging colony ships is a pain for me, so being able to simply purchase outposts simplifies things and allows me to be somewhat flexible. The only things I'm not overly fond of are the fact that they start with Gashgnasts (sp?) and the fact that they start with a seeker hero. Just give me a guardian or overseer please!