If you inspect the original language texts of Christianity (and thus, Judaism), there are literally hundreds of thousands of differences when comparing the various readings across all of the copies, for instance. There is great evidence of change, even among the selection of books for inclusion in the canon, from centuries before Christ, and for centuries after Christ as well. You can even witness differences even among the varied English translations.
The message of Christianity does depend on fidelity to what the Christian god actually said word-for-word, because the end-reward for most of orthodox Christianity (salvation) depends on faith in the message of those words. Since the Christian disciple cannot verify for himself the events and much of the claims which were recorded and upon which he is required to believe, he is dependant even moreso on blind faith. Therefore, things like verification of source, author, transmission, dating, translation, etc. matter a great deal when it comes to Christianity, because one change can alter the object of the Christian's faith, and potentally cause the loss of his end-reward.
On the other hand, the early Buddhist does not depend on the fidelity of the recorded words to the originals or what Buddha actually said word-for-word 2,400 years ago or so, because the end-reward in Buddhism (enlightenment) does not depend on belief, but on personal practice. The Buddhist disciple is expected to test for himself what was recorded, and to practice and trust what works (that is, what he directly knows for himself through personal experience). E.g. It doesn't really matter for us as Buddhists to have faith and believe that the Buddha himself actually taught the Four Noble Truths regarding suffering. It matters far more that we personally understand and know suffering and its resolution directly for ourselves; whether or not the Buddha said those words himself is mostly irrelevant. Therefore, things like source, author, transmission, etc. are decidedly less important to Buddhism, nor are those qualities needed.