If you describe an argument as "going around in circles," it's repetitive and frustrating, and nothing ever gets accomplished.
There are few things more exasperating than going around in circles; no matter how many times you try something, or attempt to explain your viewpoint, you end up exactly where you began. No progress is ever made when you go around in circles. When someone talks in circles, there is the same lack of clarity or forward movement — in this case it may be deliberate, as when a politician doesn't want to answer a question and instead talks in circles.