On the other hand, I don't think rhetoric matters more than facts. At least in my country, most of the arguments in the debate have to be based on some data/studies to be taken seriously. You still have to be a good speaker, of course, because you have to get the point across, but you can't win the debate without a prepared case just because you are charismatic.
Lots of times we had to argue for both sides during the tournament; the topics were chosen accordingly, as not to be "solvable". Of course in normal world you probably want to find some kind of compromise, but to be able to do that, you have to assess what each course of action will achieve. And debating helps you build the skillset to do just that.
For example, most of the debates we have done in high school we did from both sides; I don't think the general message was supposed to be "just argue loud enough and you'll be right", but rather "hey, look at this problem from these two sides. Crazy how both of them are partly true, isn't it?".
I think the human default is to stick to whatever your opinion is at the moment. Most of the people will never look from other POV. Maybe they won't even realise that the other POV can be right, when they are so sure they themselves are right.
I agree only if the debate's intention is to declare a winner and a loser. Having a formal session to discuss topic with opposing sides allows for well-planned arguments. OFf-the-cuff discussion, while useful, can only get you so far.
Taking a topic, splitting into two teams and fighting it out with words until the victor remains is the exact opposite of what you want to do to reach any useful conclusion on any topic.