I have mixed feelings here, but mostly going for X-2.

"The Yuna" in FFX-2 seems like a deeper character to me than she did in FFX. She's more entertaining and less of a useless character than she was in FFX (Whenever I had her out in the field, she acted as a nurse or simply the one that got the aeons on the field). She also had her hair done

With Rikku I was slightly disappointed. She seemed WAY to ditzy for her own good. However, I came to overlook this and found a deeper reason for this: she's a party girl!

Paine....she's good in battle and adds a little mystery with some dry humor.