Thank you for the question on New Living Translation, “What is the best revision of New Living Translation, 2007 or 2015?”
If one was to choose between 2007 or 2015, I would prefer the 2007 translation.
The critical issue is not the translation, but the purpose of using that translation. For simple reading, the 2015 is better, but for study the 2007 is better. I prefer using the New American Standard Bible which is more a literal translation of the Hebrew, Aramaic, and Greek text rather than a dynamic translation or giving the sense of the meaning of the passage. The dynamic translation as the NIV is affected by the translator’s interpretation of the passage.
SUMMARY: If one wants a simple reading, the NIV is good, but if one a more critical study then I would suggest the New American Standard Bible.
-Kingston