Hi there, I was a third speaker in World Schools debate style debates while in high school, and I definitely used a more aggressive speaking style than other speakers on the team as I was entirely a rebuttal speaker in this style of debate, and my personal style was also rather forceful as I made my points. However, debate is also about finding your personal style of argumentation that reflects your thought processes, energy and personality. If you are more of the calm, professorial sort you can also make your points very effectively, if not more effectively than a firebrand speaker if that isn’t your style. While poking holes in other people’s arguments is likely to make you sound more aggressive, that needn’t be the only way to do it. Perhaps give both styles a shot and see which suits you better - whatever you are most comfortable with is probably your best bet.