When it comes to duelling, Harry would definitely outsmart Hermione. Remember, Harry got an outstanding in DADA while it was the only subject where Hermione didn't score an outstanding in O.W.Ls.

I would bet on Hermione, she is a powerful witch, and she is wiser and has more knowledge about magic than Harry.

But in real time, if it was a friendly battle and not a real wizards duel, Harry would win because Hermione will never hurt her friends.

I would say Harry. After all, he did end up becoming an Auror and Head of the Magical Law Enforcement office.

Harry. Dueling isn’t just based on head knowledge, it’s also about just general instinct and experience. Harry has the better of the latter, so while Hermione is incredibly smart, this one goes to Harry.