(1) 三个短语意思基本相同，常可换用。vacillate between指“在……之间摇摆不定；在……之间拿不定主意”，后接名词、动名词，为正式用语。

• For weeks, she vacillated between a home in the city and one in the country.
  几周来，她为是在城里安家还是在农村安家拿不定主意。
• Some voters are still vacillating between the two parties.
  一些投票者仍在两个党派之间拿不定主意。

（拓展学习：小词详解 | vacillate）

 (2) hover between为“处在……之间；在……之间动摇/摇摆”，后接名词、动名词。

• I'm still hovering between the concert and the play tonight. They're both very attractive events.
  我仍然在今晚的音乐会和戏剧之间举棋不动，它们都颇具吸引力。
• After years of hovering between buying and renting a house, we at last decided that it was better to own property.
  经过多年的在买房还是租房之间的举棋不定，我们最终决定还是拥有产权好些。

 (3) waver between意为“在……之间犹豫不决；在……之间动摇/摇摆”，常用进行时。

• She is wavering between staying single and accepting his proposal.
  她犹豫不决，不知是继续单身好，还是接受他的求婚好。