The score contributes hugely to how epic the Duel of the Fates is. You also have one of the cooler looking villains in Darth Maul, the introduction of the lightsaber bo staff, and the first time they were really able to do elaborate, high speed choreography for a lightsaber fight.
As for Qui-Gon's aggression, he did use an aggressive form of lightsaber combat and was also something of a maverick. He didn't fall in line with all of the teachings of the Jedi. Then there's the fact that his master was Count Dooku. So some aggression shouldn't be surprising, he just would never give himself over to it. I also think he felt a need to protect Obi-Wan in the fight. I don't see it as him leaving his padawan alone. I see it as Qui-Gon trying to keep Obi-Wan away from danger and end the threat himself.