https://www.youtube.com/watch?v=BrKeGHwOBvsI simply feel it most represents what I would like to feel during a champion battle. The beginning is full of wonder. You made it here, you're finally confronting your final challenge. It's not some scary villain, either, but a friend who has helped you along the way.
But as the song progresses you start to realize that it won't be as easy as you thought. The trials of the battle begin to take its toll and the pace kicks up, you may lose a Pokemon here and there, she gains the upper hand around 0:49. But you take it back at 1:00.
I love this idea of back and forth and at 1:14 you're once again reminded of where you are. Finally, after all this time... Fighting for your right as champion.
Cynthia's is good too.