Yuna's voice acting was SO MUCH BETTER in X-2. Part of it, though, had to do with the plot. I mean, in X Yuna always sounds breathy and weak, but that's because...(do I really have to spoiler this? ahh, fine...) (SPOILER)she's marching to her own death for 90% of the game. In X-2, she's free from that, and therefore living a more carefree life, and her change in tone reflects that. But it's just so much nicer to hear.