Difficult choice for me between Ahmed Deedat and Dr. Naik. I voted for Ahmed Deedat, but believe that in a few years if not sooner Dr. Naik will surpass him.
But, overall, you know those who truly debate Islam in the defence of Islam and to spread Da'wah are not engaged in any contest. I am certain all great debaters would consider the others to be superior to themselves. They are the ones who are truly facing Jihad and they are the ones who will be the protectors of Islam. From them we all can learn that it is much harder to live for Allah(swt) than it is to die for him. In my opinion that is where the Jihad for this era is to be fought and won.