I chose Doug because I didn't see Carley as valuable (having said that, my hubby chose to save Carley because she had already proven to be a great shot). Doug had smarts and tech abilities. I thought about the fact that he might be able to rig up some sort of power system when/if the lights went out. (LOVED the alarm system he set up)!
He seemed like a better person, a more interesting person. Carley seemed... eh. :P lol I do like her, too, don't get me wrong, just preferred Doug.