1) debate as a class or sport: these debates occur in certain places like school or community centers that are set our specifically for them. The purpose is to argue for your side. it doesn't always help arrive at a better decision because false information can be presented if it isn't caught. the debate is structured. i don't know how it affects the decision making process.
2) Court: these debates occur in courts. The purpose is to prove to the judge and jury that your side is right. it almost always helps arrive at a better decision. the debate is structured. it effects the decision making process because depending on the facts that are stated the jury must make a decision.
3) just in between friends: pretty much anywhere. The debate serves the purpose of different people with different opinions arguing to show there point. most of the time the people are both stubborn and unwilling to make a decision. it is unstructured. it effects the decision making process if one of the parties is willing to give in.