The way I think about them as characters (who knows about RL) is that Nate is a planner, he's always got a long-term goal and the big picture in mind. But Brad is a do-er. Give him a goal and he'll map a route to it, he'll execute beautifully. It's not that he's uninterested in the big picture; he just finds a lot of satisfaction in meeting the needs of the now. :D