See you! or See you later! Is a very friendly way to say goodbye and it indicates that you are going to see that person again soon. Bye now is kind of neutral but when I hear it, it is usually from a friend who is not very close to me. Someone who I don't see often but we are still polite.

这能有什么区别。see you 暗示了不久之后会再次相见吧。 bye 没有这个意思。