Mani Ratnam, the director of the two movies, is a Tamil director who is aiming to reach a larger Indian audience. He made two versions of the same movie, one in Hindi and one in Tamil. This widened the audience for the movie. Ratnam has attempted this sort of feat with previous movies, mainly by dubbing his Tamil language movies into Hindi. However, there are nuances that this sort of dubbing misses and he made two different versions of the same film.
The two movies are based on a story line taken from the Indian epic, "The Ramayan." The Ramayan is the story of Rama and his wife Sita. Raavan, or Raavanan, is a demon that abducts Sita and keeps her in captivity in a forest. The epic tells how Rama rescues her from the clutches of the demon. However, he is not convinced about Sita's chastity after the rescue and subjects her to tests. "Raavan" and "Raavanan" offer a more modern perspective on this basic story line.
One major difference between "Raavan" and "Raavanan" is the cast of actors. In the "Raavan" version, Abhishek Bachchan plays the lead role of the kidnapper, representing Raavan the demon. Vikram, a Tamil movie star, plays the role of a cop, representing Rama from "The Ramayan." Aishwarya Rai Bachchan plays his wife, representing Sita. For the Tamil movie, Vikram plays the Raavanan demon role, and Prithviraj, a Tamil actor, plays the role of the cop. Aishwarya Rai Bachchan plays the heroine in both versions.
Music is a major attraction for Indian moviegoers, and another difference between "Raavan" and "Raavanan" is the music. While A.R. Rahman has scored the music for the two versions, the songs for the two versions are written by two different lyricists. The Tamil version's songs were written by Vairamuthu, a Kollywood lyricist, while the Hindi version's songs are by Gulzar, a Bollywood lyricist.