While I agree that the redhead looks more agressive, it's usually not a good idea getting fooled by only looks, as they could be deceiving. There's nothing more dangerous in this world that someone who looks calm and cheerful in "daily life", because when the right (or bad xD) time comes, they become the worst nightmares for anyone on their way.
And considering that physically they're not that different (being curvier doesn't make you stronger xD), it's not easy to tell who would come out on top of this.