"Debate" tends to be no one listening to anyone and every one arguing trying to "prove" their view. It's seldom yields any good fruits, and I try my best to avoid such.
From my perspective, that is more the definition of an argument rather than a debate. A debate can be a good thing. In high school and college there were organized debate teams and they competed against other schools. It was absolutely necessary to listen to the other point of view in order to counter it with a meaningful reply. So there is a difference between a debate and an argument. Again, just my point of view.
What is the purpose of debate?
The purpose of a debate is to discuss a controversial subject in a point/counterpoint manner by using facts and philosophy. It doesn't always have to become a nasty argument. In fact, it never should. Again, a proper debate can be a good thing if all sides remain cordial.
What have you learned personally from debating with other Christians?
I have learned others point of view and their reasoning behind it. If I lose the debate, I have gained more than my opponent! Think about it... If you are shown to be wrong you are the one who has learned and benefitted the most. If I win or it's a draw, I have learned more about the other side of the issue... If it's a good debate, chances are I had to dig up new facts or support.
What is your favorite part about debating?
I generally don't enter debates unless I am interested in the subject. Therefore, I like to discuss things I am interested in.
The least favorite part is when it does become an argument and it becomes personal.
I haven't debated in a while... There haven't been any subjects that have come up lately that I haven't been through countless times. Furthermore, I sense that some topics becoming an argument is unavoidable with many folks.