Yuna FFX-2: I like the guns.
Eiko: Summons stuff and heals stuff. perfecto.
Paine: Swordy swordy swordy sword, swordy swordy swordy sword...
Lulu: Blasts stuff. Also perfecto.

Thats my choice number one. Choice number two is...

Rikku FFX: Steals stuff and mixes stuff.
Aeris: Just... So... Cool.
Quistis: Go Blue Magic!
Celes: Hits stuff, heals stuff, and blasts stuff.

Choice number two is above. But, the perfect party is....

Rikku FFX
Eiko
Lulu
Celes.