one in a million 和one out of a million有何区别

两者区别不大：one in a million = one out of a million,本意是“每百万...就有一个/百万分之一”,只不过前者可以引申为“凤毛麟角,百/万里挑一,佼佼者”的意思.
例如：
1..I want to introduce you to a person who is one in a million.
我要介绍给你的人可真正是百里挑一的啊.
2.The millions are awake enough for physical labor ; but only one in a million is awake enough for effective intellectual exertion ,only one in a hundred millions to a poetic or divine life.
几百万人清醒的足以从事体力劳动,但是一百万人中,只有一个人才清醒的足以有效的服役于智慧;一亿人中,才能有一个人,生活的诗意而神圣.
3.Only about one out of a million cells will correctly incorporate a foreign gene using the most common versions of this technique.
应用这种最常规的技术,仅有百万分之一的细胞可以正确加人外源基因.