This one is a no brainer. Azula would kick some serious butt. While Bloom has her silly dragon fire, Azula has apoy and lightning. She has two elements, not just one. And she's an expert at using both. Unlike Bloom, who was completely hopeless and confused as to how to user hers. Moreover Azula was a child prodigy, she mastered 14 forms of firebending near age 8. Bloom didn't even know she had powers at that age. That said, Azula has far madami experience. She's been working with her powers far longer and has had the skills to use them far longer.