Religious debates often seem to be like a football match, or any other competitive sport.
Broadly speaking there are usually two groups of 'die-hard supporters' that attend either event.
In sports it is usually the home team supporters versus the away team supporters. While in a debate about religion it is usually religious people versus atheists (or sometimes a different religious/spiritual group).
Much like supporters at a sporting event, the supporters in these debates - atheists and religious people - go to see their team/group win (or more accurately: to whoop the butt of the other team).
There is of course a big difference between these two events. In sport, whether the result is a win, loss or draw, the final result is obvious for all to see. Barring a draw, one team has more points or goals scored than the other team, therefore the winner is clearly defined.
Sure there will be people claiming that the awful umpiring won the other side the match, or that one team played unfairly, or some other excuse, but the final result will still stand.
In a typical religious/atheist debate there is no (at least not a very accurate or agreed upon) way of 'keeping score', or knowing who won. The result will be subjective. Usually the religious supporters will see all the points that their team 'scored' and ignore the points of the atheists, and vice versa.
Atheists will think that they have won the debate, and religious people will think that they have won the debate. Neither side is likely to think that the other side is actually a better 'team' and switch allegiances.
Does this mean that debates between atheists and religious people are a waste of time?
Like most sporting events there will be a few people that attend these debates that may not have an allegiance to either side. The question for these people would be: are these debates actually a good way of ascertaining whether a particular religion is right or positive, or if atheism is the way to go?
The debates are hardly an exhaustive examination of either side, and rarely do they consider ideas that lie in between established religious/spiritual ideas and atheism. It really feels as though it is a PR exercise to make both supporters feel good about their own 'side'.
But if there is a chance that just one good argument out there can change the thinking of a handful of individuals that are somewhat on or near the fence in regards: to religion, atheism or spiritualism in general, then you cannot literally say that they are a complete waste of time; even if such debates are unlikely to change our own way of thinking.