First off the reason the battles are "ssssssssssssllllllllllllooooooooooooowww www........"
is because it uses a wait system while FFX-2s is a ATB system.

I hugely prefer Rikku in X. In X-2 she was alright, overly hyper but it was fine- not good not bad. In FFX she had a range of emotions and feelings not just over the top energy, she had that excitable joking around mode (which I thought was way better done. She also had a serious side too, making her my 2nd fave character in FFX and 2nd fave in X-2 (though that's because if lack of competition she'd come in 5th or something in FFX with her FFX-2 character).