Aiko Tachibana is a determined character but I dare say that she isn’t quite close to being more determined than Uta. Uta was able to plunge ahead even while she was by herself for a super long period of time. Aiko never had to go through such a trial. Perhaps Aiko would have been able to tough it out but we just don’t know while we actually got to see Uta persevere. Aiko has no defense against Uta’s songs and would go down quickly. Uta wins.