The final trait you must look for is temperament. I say final because that will not be evident until the hormones flow. For example, Isaac had one brother who was larger than he was. Super, super friendly cockerel (called him Mr. Friendly) loved to sit on Tom's knee. Sweet boy. Comb wasn't as nice as Ike's, but not terrible. Markings were not quite as good, either, but oh, the size on that boy! As they approached 14-15 weeks, he began attacking my shoes. He'd bite, then he actually spurred Tom one day. Isaac had never been super friendly, but not skittish either. His markings were superior, he was catching up in size to his brother, and after he learned not to bite about 12-13 weeks old (I grabbed him up and held his beak and it took two times, then he was cured-hasn't bitten me since), I knew he was truly my Rockstar of the group. When I removed the last two cockerels so they wouldn't be a bad influence on him (the third one had begun the shoe-biting thing, too), he became this calm, well-mannered sweetheart that he is today.
You'll start seeing their final temperament when they're 15-20 weeks old and are really after the ladies.