It seems like Evacuating Zion is actually the best ending as far as the ending slideshow goes, but it demands EXTRA work for it to actually turn out well; if you neglect doing all that's possible to help Daniel, then it's actually a suicidal trip for the Sorrows. It also has practical downsides: taking Graham's advice leads to an enemy-free Zion, as far as the White Legs go (the main enemy), whereas taking Daniel's means that one of the good tribes leaves. If you mean good in what's best for Zion, probably following Graham and convincing him to have mercy on the leader of the White Legs. If you mean good as in the best ending slideshow, then Daniel's with all of the side quests complete.