what day is your favourite day?what's your favourite day?之间的区别.

what day is your favourite day?what's your favourite day?之间的区别.
想确认下两者的回答没问题吧?what day is your favourite day?一般回答It's ...what's your favourite day?一般回答My favourite day is ...
除了回答之外还有什么区别和注意的地方?
what day is your favourite day？这是外研社课本当中的句子。有没有哪位高手可以帮忙下？