Valmiki’s Ramayana would have been the narration of Sita Ma, since she was left with the Maharishi during her pregnancy and childbirth, which were the most challenging times for Sita.
Therefore covering the life of Rama since their marriage with all its challenges as a first person perspective and most intimate and authentic experience.

Hanumanji comes into Sri Rama’s life during his 14 year journey, but the journey to Lanka and the war itself, the journey back and being most intimate to Sri Rama and Sita Ma can be best narrated only by Hanuman which Sita Ma would not have access to.
But Hanumanji as a witness, bhaktha and a supreme Yogi, would have known Mano-Gati of Sri Rama and therefore his Ramayana would have been more inspiring and touching.

The only way to have access to that Ramayana, is by becoming the Bhaktha of Hanuman as he revels in the Rama we haven’t seen and reveals the Ramayana that we have not known.