Ved-vs-Purans

Ved and all its associated scriptures [Vedangs, Brahmans, Aranyaks, Upnishads], plus Darshan-shatras describe rituals [Karm-Kandas], essential philosophy, prayers to various deities. However, their main purpose is philosophy [Gyan].

Puranas are generally speaking of TWO types -- Historical in nature and stories with the purpose of developing Bhakti in people. Harivans Puran is historical where as Devi Puran is for Bhakti. In Historical purans, God doesn't appear when a discipline does pooja [tap]; whereas in puranas that intend to promote faith in God, God appears very quickly, gives boon [vardaan] to the person doing tap, punya is rewarded quickly and paap is punished quickly too. The relationship between karm and Karmfal is shown explicitly and quickly, this drives masses to Bhakti -- pooja-path.

Both have their purpose in society. On one hand we find many Rishis spending their lifetime capturing Gyan in the form of Veds and related scriptures including Smritis, adding commentary to Upnishads etc. Rishies in this category are many -- Yajnavalkya, Manu, Vishwamitra, Vashisht, Adi Sankarcharya, Ramujacharya, Ballabhacharya, Vivekanand and so on. Bhagwan Vyas falls in this category as well as he wrote or compiled many Purans as well.

Most of these, so called Dharma Gurus of recent time, tell stories from Purans. This is not necessarily reflective of their lack of knowledge of the essence of Vedic scriptures, but also due to the need of present times. The audience needs stories to be motivated to get to the essence. These gurus are serving a big cause of Sanaatan by keeping majority of less sprititually aware masses engaged and live a life of Sanaatani, even if they don't study scriptures. One day, these masses can be upgraded to read vedic scriptures with deep philosophical meaning.

Similarly, other scriptues aslo have different orientations, though telling the same story/ historical events. For example:

• Bhagwatam, Maha Bharat, Bhagwat Puran and Harivans Puran -- All these cover same subject, same time [kaal] but have different perspective because of different objectives. A few links on this are: 
  • Basic Difference in common language on YouTube
  • On Webdunia, in Common Language
• Valmiki Ramayan and Tulsi Das- Ramcharit Manas -- Similar variation. A few links:
  • By Ashish Gupta
  • YouTube Video by The Hindu Saga
  • By Ajay Gautam
  • YouTube By Shankara Bharadwaj and Anand Prasad on Sangam Talks

Efffect of Story Telling in the long term: Though no rigorous scientific [in modern terms] have been done to answer this question, here are my opinion:

• Positive: Keeps the story alive and this faith on Sanaatan Philosophy on-going. Society resisted on-slaught of invasion by Abrahmic religions. 
• Positive: Provides an opportunity to educated massed on deep Sanaatan Philosophy that is bring back the crux of Sanaatan Civilization. If not for this, almost impossible to undo the damages.
• Positive: Enables people to people interaction and some cohesiveness of thoughts.
• Negative: Masses flock to any place that is called GODly by anyone e.g. Majaars including Ajmer Sheriff etc., Sai Shirdi Baba, anyone putting a Stone with some sindoor etc [remember PK cinema], doing any ritual for removing bad omen or for getting some rewards. Overall, breaking the link between Karm and Karmfal.
• Negative: Many people consider these stories as an end in itself and don't comprehend the main philosophy. For them, getting to actual philosophy effectively becomes Un-learning the stories and then learning the philosophy. A quite difficult task.
• Negative: There are many stories which are seemingly contractory [due to contextual differences] which confuses people a lot and then people justify their actions using these stories as convenient. For example, a saying -- nothing moves without will of God, can make people so lazy justifiably. Another example of Gaj [the elephant] and the Magar [the crocodile], one interpretation: as long as the Gaj felt he was strong, God didn't come to his rescue, when he gave-up and surrendered, God came and saved his life. Such explanation justifies people's in-action. [Philosophically, the interpretation should be: The Gaj first tried his best and then asked for God's help, when it was beyond his capacity.]

Since story-telling has been going on by so many Sadhus for so long that most people today think that to be Essence of Sanaatan Dharma and serious teachings by even modern saints - Shri Dayanand Saraswati, Shri Pandurang Shashtri Athwale, Vivekanand, and philosophical aspect conveyed by many others.