I voted for the duo, even it doesn't seem v popular here lol...
I think it's more difficult to sing in duo : different voices, so the two ppl have to have some chemistry as in lakorns lol, for the song to sound v good. Plus the voices are different it requires more efforts to adapt a voice to another one.
Omg it could b very sexy to hear a duo, i'm more a fan lol...
But me have a question : how do u judge ?