区别就是两者意思是不一样具体的不同如下

on holiday中文意思是

假日在休假中在度假

例句

It takes the gilt off the gingerbread when you arrive on holiday only to find that the room you've booked has been allocated to someone else.

你假日到达旅馆，却发现自己定的房间分给了别人，那才令人扫兴呢。

in holiday为错误搭配使用