People arguing why can't we have versus thread for legends. I believe there could be and my dad and I used to have the same for getting to know the traits and characteristics of these singers/actors/actress.
In my opinion Mohd Rafi was way much better singer than Kishore Kumar. Rafi got one of the toughest songs in Bollywood and performed excellently for e.g. to sing "O duniya ke Rakhwale" He took such a high node that blood came from his throat. Rafi made 60s a classic era for Music of India where the movies used to get silver jubilee only if Rafi and Sahir's songs were there in the movie. When Lata and Rafi fought over the songs, Rafi was still hit with Suman Kalyanpur and hence Lata has to comeback for negotiation.
Though the biggest fan base currently belongs to Kishore and he was such an impromptu singer that he could add anything, any style and even useless words as well. His personality was charismatic and that refers in his singing.