That is for you to decide这里加FOR和不加在语法上有什么区别

有一个固定搭配：sth. is for sb. to do.你说的that is for you中的that是代词，指代sth.要是不加for，就要用定语从句了：That is you who to decide…。所以，在一般主系表形式的句子中，要加for.

语法上?
说That is for you to decide,可以解释为"'什么东西'或者'什么事情'需要你来决定."强调的是事物.
说That is you who to decide...,比较强调这个you,主语,解释为"这就需要'你'来决定什么事情"