Come at me.

Let's seriously examine this for a second. I noted back when i played FFXIII that it was trying really damn hard to be different from XII. The linearity is one major difference of course but the other is how both games deal with their cast.

Let's face it - FFXII did a horrible job with its party. Party members are largely irrelevant for most of the game, with Fran, Vaan and Penelo just taking up space. Basch suffers that too as after Vossler dies, he becomes totally superfluous until the frickin' final dungeon. Balthier too only does anything of note once you reach about the halfway mark of the game. Ashe is the only consistent character.
No, the real stars of FFXII were the antagonists. They moved the plot, they got most of the character exposition and development, and the whole game was really about them.

FFXIII averts this by having three, maybe four, antagonists and they only come into play like 10 hours or so into the game. And even when they finally do show up, they don't stay very long at all whereas every other cutscene in FFXii showed the bad guys.
Final Fantasy 13 is definitely a game about the heroes and how the heroes are dealing with the crappy situation they find themselves in. Not once does any of them feel out-of-place or unnecessary and they all get some development.

Vanille > Penelo - Duh. Vanille is sexier and actually matters.

Hope > Vaan - Vaan has a terrible voice and design. He also does nothing for most of the game except serve as comedic relief.

Sazh > Basch - only because Basch does jack for damn near the entire game.

Lightning < Ashe - Although I will admit, Lightning being the first main female with no love interest whatsoever is something. Shame everything else about her sucks and Ashe beats her in voice, look, motivation, backstory...

Snow = Balthier - I liked them both. Snow did more for the plot but that's just because FF13 treated its party better. Once Balthier actually does anything of importance (ie. once you head for Archades) he helps shape one of the best subplots in the game.
They're also alike in that they both have orgasm-inducing voices. And don't forget their common bond of being confused as to their role in the narrative.

Everyone in FFXIII >>>>>>>>>>>>>>>> Fran. Fran is garbage, pure and simple. At least Feng actually succeeded at her fanservice. Fran's voice was so terribad that it ruined any attempt at sexiness and she was only in the game for that "sexiness."