Based on the photos, showing the relative size of the actresses who play these characters in the film, it's easy to see why some would vote "Dale" over "Aura."
But you must! (that's an order) remember that Princess Aura isn't some spoiled little hothouse flower, she's the daughter (and heir apparent) to "the most ruthless dictator in the Universe!" Certainly a heavy burden for a Princess to bear, but wouldn't she have, from birth, have been tutored in how to be "ruthless" in order for her to be prepared to assume the mantel of leadership in the (likely) event one of the many revolts against Ming The Merciless were to succeed in separating the old boy's head from his shoulders?
I think so!
Her military advisors would have taught her all the ways in the Universe to fight.
Others would have shown her (doubtless in sessions in the Imperial Dungeons using prisoners as 'teaching aids') how each of the different species under their demonic control could be hurt and/or disabled in fights; which body part was most vulnerable; which yielded the most pain and how to attack each, while defending herself against the others strengths.
Dale Arden was a (lab assistant?) to Dr. Zarkov IIRC, not anyone trained by experience or education to fight for anything except next to use the Bunsun Burner (or a beaker)? Even if she had the size advantage her actress enjoyed, I doubt "Dale" could beat "Aura" in any fight where it meant something to "The Next Merciless Emperor of the Universe" (cue theme music)
