Yuna was...a big fake. It's smarter to say "stupid" than "cool" acting like someone she's not in the first place. She was irritating all throughout the game acting like she's this cool rocker chick.
Rikku was...obnoxious. Her attitude was way exaggerated. She was better in FFX. She may have been childlike but still retains some essences of maturity.
Paine's cool!