When I was playing the game, i was actually disappointed she only appeared in the first level...
against each person. (and if for the person that they don't really 'relate', I'll basically say something about what I thought did or didn't make sense in comparison to Lebreau)
Vanille
I think her design is more interesting than Vanille's. (not to mention she doubles as a pseudo white mage with her potions.)
Snow
her weapon makes more sense than Snow's in the sense that your coat can magically make you able to punch a robot's circuits out, and Snow being the leader of Nora made... little sense, Lebreau seems more level headed and suited to that role, while Gadot and the others are better for the grunt work.
(except the kid, he seems to just be a random kid they picked up.)
Gadot
She uses her firearm in a much more realistic manner than Gadot, but she does slightly show off with her battle stance, which in turn is reminisce of Blank from FF9 (who happened to be my favourite from FF9) which automatically boosts her rating in my books.
Fang
Main thing that Lebreau has over Fang is the fact she doesn't have a random australian accent, but in terms of personality, the two are similar and I imagined Lebreau acting similar to Fang if she was kept as a final party member.
Lightning
She has personality and isn't a cross between Cloud and Squall.
Hope
I don't really get why Hope was kept as a proper party member, sure, he wanted revenge, but, I found his whole story and scenario forced, and basically, I just like Lebreau more than Hope.
for Lebreau, I thought that her role (shown mostly in flashbacks) showed that she was responsible and had abilities to raise funds for operations and keep account of other aspects with the shop and how she acted more mature than other people, ie, Snow.
<anyone else hoping he'd actually use Lightning's knife? I thought he could have 2 knives that combine into a boomerang or something...>
Sazh
...I just didn't like Sazh... at all, he'd basically a skinny Barret, except for Cid's past with a ridiculous Afro-being-a-bird-nest idea that probably started as an office joke, that they kept in the game because it was 'funny'.
plus, how do two handguns turn into an assault rifle!?
as for the Nora being used as a plot device, personally, I think it would have been better if NORA was just people on the purge train that decided they didn't want to go and acted up, since thats all Nora really became in the end.
but, Lebreau was shown saving Serah from monsters and chiding her and saying that she had to look after herself, i want the ability to talk to her more often if nothing else. *_*