Outcasts. Sloane is a piece of shit and she hates the Alliance, but at least she can be reasonable some of the time. And she's also pretty predictable. With Reyes, he's shifty and sneaky as hell. You never know what he might try to pull on the Alliance or anyone else. And you never know when he might be lying or working an angle. Sloane sucks, but she's not as bad as Reyes

The Outcasts. [spoiler]I saw the choice as the Devil I know vs the Devil I don't. Sloane's a bitch, but she wasn't always one. She has an exemplary military record and a strong sense of honour so she can be redeemed in a future ME game. Besides, activating the vault on Kadara and getting permission from her to build an outpost on Kadara effectively removes most of her power. When you first meet her, Kadara Port is the only habitability environment on Kadara due to all the acidic water so she can threaten to exile anyone who does not fall in line and does what she says. After taking care of Kadara's water issues and establishing a Nexus outpost, the threat of exile from the Port no longer means any means instant death, they now have clean water to survive on and exiles can either build their own dwellings or rejoin the Nexus at their outpost. Reyes represents too many unknowns. I can't trust him since I don't know anything about him. [/spoiler]

[spoiler]Outcasts because Reyes is a rotten double dealing scoundrel that you could never trust. Sloane might be a villain but she's kept her word so far.[/spoiler]