让开：一般用于客气的说法，闪开则有时用于不礼貌的说话中。 例：请大家让开一条路； 你给我闪开，闪一边去，别防碍我做事。

Normally, 让开 and 闪开 both have the meaning of ordering someone give way to you，and it sounds impolite when you use them directly in your daily life. Actually, 请让开 or 请让一让 is a better saying. In another meaning, when you give way to others or avoid something, they are just two verbs, and you can use them equally. For example, 救护车来了，人群中让开（闪开）一条路. or 那辆汽车没有撞到我，因为我及时让开（闪开）了。

if you want to get someone out in front of you, the first one is more politely to say, you can also said 请让开 to be more politely. the second one, in this case, will be like "get the fxxk out of my way", which is rude. hope this can help you.