The issue with Michael Newton or someone like Brian Weiss's approach is that their interpretation of reality is mostly influenced by the 'channelled masters'.
They would show up and interfer with the session (interestingly enough at the moment of in between lives). They would then replace the subject and answer questions on their behalf (which seems very narcissitic to me). It is all about why we are here and the necessity of growth through multiple lives blablabla. The casual Eastern and South Asian dogma about how reincarnation is our fault, we are not enough, and that we need to keep dissolving karma (obviously it is not said this way, but that's what it is in a nutshell)
By definition, I never trust channelled information. RV keeps the subject online and conscious, as a direct witness of the target: witnessing both the objective landscape at hand and the actors who are trying to interfer be it malevolent or benevolent (channelled masters and what not).
That's where the difference lie.
Memory retrieval is easier in a hypnotic state: but the therapist needs to be aware of interferences and not give them any space to speak on behalf of the patient. It is the opposite that needs to happen: empower the patient to stay online and describe the truth of the encounter. Which often than not is covert, abusive and patronizing, and takes the therapist off course.
Good therapists do a good job when it comes to isolating and healing human to human abusive relationships. It is no different with those off world entities.