There is no difference also between the Vedic mantras and what is explained in the Puranas and Itihasa. According to Srila Jiva Gosvami, it is mentioned in the Madhyandina-sruti that all the Vedas, namely the Sama, Atharva, Rg, Yajur, Puranas, Itihasas, Upanisads, etc., are emanations from the breathing of the Supreme Being. The only difference is that the Vedic mantras are mostly begun with pranava omkara, and it requires some training to practice the metric pronunciation of the Vedic mantras. But that does not mean that Srimad-Bhagavatam is of less importance than the Vedic mantras. On the contrary, it is the ripened fruit of all the Vedas, as stated before. Besides that, the most perfectly liberated soul, Srila Sukadeva Gosvami, is absorbed in the studies of the Bhagavatam, although he is already self-realized. Srila Suta Gosvami is following his footsteps, and therefore his position is not the least less important because he was not expert in chanting Vedic mantras with metric pronunciation, which depends more on practice than actual realization. Realization is more important than parrotlike chanting.