I would suggest that they pick two voices to represent voice of India - One male and One female voice. The voice quality of female and male singers is so different that its hard for me to compare male singers to female singers.
Imagine trying to pick which voice is better Rafi ji or Lata ji? it will be a hard choice. At least for me, I can pick a fav male singer and fav female singer and not just one singer.
my 1.5 cents!! cheers.