It strikes me that the debate format from heavyweight apologets and theologians has some benefit, but to a limited degree. On one hand, we need a public face of Christianity that will go out to the lost, including the lost in intellectual circles, and show them that Christianity is reasonable and explain the gospel. This helps not only to evanglize, but to also to reinforce the faith of existing believers who are interested in such questions. When Christians present truth in the public square it also helps to slow the decay of our society, and since some of the decay begins with ideas, presenting truthful ideas in a world of confusion helps everyone, whether they agree with it or not.
But it also strikes me that public debates have a limited benefit. Even when the best Christian spokesman goes into the world and explains truth, especially in a confrantational debate format, most of the time the other side still claims victory. Even great modern day debaters such as William Craig have noted that in public confrontations where he has thoroughly defeated the other side, their followers seem to be just as robust as ever.
Scripture commands us several times to defend the faith, to refute error, and to go to the lost and present the truth. We are told to ‘give every man an answer.” But we must realize that however well prepared our efforts are, we are but feeble humans, and without the work of the Holy Spirit, our efforts are in vain.
That said, I wish more power to those like William Craig. I was atrracted to theology and apologetics by two men of a previous generation, Walter Martin and Norman Geisler, both of whom had many public confrontations with those who disagree. The modern crop will raise up the next generation of apologists and bible defenders and indeed help strengthen the church, which is desperately weak on many theological fronts. We must only realize that public debates are of limited value, and the real work of the faith is done one on one, with the movement of God as the driving force.