We DO know that RJ was very influenced by Son House, Lonnie Johnson, and Leroy Carr, and he DID imitate very aspects of their performance. He even 'borrowed' quite a few of their songs.
It all depends on who's interpretation you like the most.
I wouldn't call Robert a 'Genius'. He wasn't neccessarily an innovator.
As far as Bobby D., his early foray into Folk was not genius. His genius was not evident until the mid-'60's, when he started to put his poetry to music, and discovered his TRUE musical voice. It was then that he slowly left "the scene", and stopped mimicking Woody Guthrie.