They are both awesome and amazing first of all! My personal opinion is that before Aelin gave up the majority of her powers, she would have easily beaten Feyre due to her immense fire power and sharp assassin skills (trained longer than Feyre), if Feyre wasn't daemati. Being daemati, Feyre could easily shatter Aelin's mind before she even makes a single move. However, Aelin may still have had a chance against Feyre before she lost her powers. Now, Feyre would definitely be the winner because she has more magical powers and due to her daemati skills.