First there is the matter of truth. Christianity provides witness to the death and Resurrection of Christ, denied by others. Jesus Christ is the author of Truth.
Gospel of St. John:
31 Then Jesus said to those Jews, who believed him: If you continue in my word, you shall be my disciples indeed.
32 And you shall know the truth, and the truth shall make you free.
33 They answered him: We are the seed of Abraham, and we have never been slaves to any man: how sayest thou: you shall be free?
34 Jesus answered them: Amen, amen I say unto you: that whosoever committeth sin, is the servant of sin.
35 Now the servant abideth not in the house for ever; but the son abideth for ever.
36 If therefore the son shall make you free, you shall be free indeed.
37 I know that you are the children of Abraham: but you seek to kill me, because my word hath no place in you.
I am an eastern Catholic (Byzantine Greek Catholic) which takes a mystical approach however used within a rational framework.