Eugenides has more experience, even if he was never in the Hunger Games.
Tricky. Eugenides is likely a better swordmaster than Alanna, but Alanna has magic. How much of an advantage would that be, exactly? Would Eugenides be clever enough to nullify its effects? Could either of them really take down Katsa?
Eugenides, for one, has all her skills but relies on his brain instead of instincts. But if Howl's and Hermione's magic couldn't take out Katsa, then how could Alanna's? Especially with the armor?
Eugenides is probably faster and might be able to doge Katsa long enough for her to slip up.
Aragorn is a better swordsman, but Alanna is a more powerful mage. Or at least, she has more practice with it. Sadly, Aragorn's talent and power comes from his leadership of others, where Alanna is the sort that "finds dark places and fights in them alone."
Sabriel might have had a fair chance of taken Katsa down if she had enough time to draw her bells. Tally might actually have been fast enough to do the same, if Katniss weren't so good at hiding.