I think Harry has more natural talent, especially when it comes to dueling. But Hermione is clearly smarter than Harry and has enough knowledge about the magical world and just plain common sense to equal Harry's abilities. I think that both Harry and Hermione are incredibly good at magic and neither one is better than the other. They (along with Ron, of course) are both essential to the trio. Harry's skill is no good without Hermione's intellect and vice versa.