The NT, moreover, was written almost esclusively by Jews, whose "strict monotheism and traditional intolerance of syncretism" would have militated strongly against any wholesale borrowing from pagain cults.
But the fundamental difference is the historical basis of the Christian faith over against the mythological character of the mystery religions. The deities they proclaimed were no more than "nebulous figures of an imagineary past," whereas the Jesus of the apostolic kerygma has a historical person who had lived and died only a very few years before the first NT documents were written.
The mystery religions essentially celebrate a dying nature god who then, like the coming of spring, is revived or reborn. There is all the difference in the world between this and the resurrection "on the third day" of a historical figure to whose resurrection appearances many could testify from personal experience.
It is significant, moreover, that the references to a three-day gap between death and revival that we find in regard to Attis (possibly Adonis according to one account) and Osiris cannot be dated earlier than the second century A.D., while the tradition about the resurrection of Christ on the third day, as recorded in 1 Corinthians 15, can be traced back to well before the middle of the first century.
So, if borrowings were made from one religion to another, it is tolerably clear which way they went.