I will be going the route of Purity.
Basicly I always tend to play "Humans" in all games I play, be it Fantasy/Sci-Fi/etc, and/or computer/console/pen and paper rpgs/table top/other types of games. The reason I like to play human is partly because I am human my self, but also because the general feeling I get from humans is that they can be anything and do anything they want... not limited or pigeonholed into "this is how this race is, and they do not go outside of it often, if at all".
Humans in games tend to always be the jack-of-all-trades type of race, and I like that, I like to have my options open to go in any direction I want without having to worry about some kind of large limitation in one or several specific areas, be it something physical, mental, or what ever. Yes, other races might be superior in certain aspects, but at the same time they are limited in others. So even if it might be better for me to choice a race that is more combat oriented (I always tend to go the combat route when I play games) so I can be really good at it... I still prefer choosing a human and being good at combat, but still able to be good at all other things to.
So since Purity starts out as Humans, and ends as Humans, that is where I will be going... as I am conquering all other factions on the planet.
I have to say though... I was a bit dissapointed when I found out that this game is basicly going to be almost exacly as Civ 5 is. Now don't get me wrong, I really like Civ 5, I have played it a lot, and tend to go back and play it fairly often (last time being last week). But when I for the first time heard that they where making Civ Beyond Earth I imagined something compleatly different. I basicly imagined a game where you would be in space, exploring and fighting over either solarsystems or even galaxies as you went along. Not that it would take place on just one single planet somewhere out in the galaxy.
Now of course there are games like that out there, and one that is pretty recent (which I do not recall the name of right now)... but I wanted Firaxis to make a game like that, wanted their take on such a game. So yeah, a bit disapointed. I will still play CBE, and probably a lot of it... but I am uncertain if it will have the same staying power for me, like Civ 5 has had.