I found that the characters provided a good balance in this game, with all of them being an important part of the team with the possible exceptions of child Rydia and, of course, Edward. However, in terms of overall value added to the team I am going to have to go with Rosa as number one. She is the main healer of the game and many of the later boss battles could quite simply not be won without her. I can't say the same of any of the other characters. Her heal spells and buff spells are unmatched in terms of keeping your party alive. In non boss battles she deals decent physical damage with bows and can also throw out the occasional Holy if you want to do a bit more damage. Her defense and HP are low but not as low as Rydia's and in the back row she can take a few hits.

Second place is probably a tie between Cecil and Rydia, with an honorable mention going to Yang. Rydia is obviously the best damage dealer with her final summons. Asura can also heal in a pinch if you get lucky, but she is physically weak with low HP and defense which makes it harder to keep her alive to tear stuff apart with Bahamut. But if you want to end a battle quickly, she's the one to use. Cecil has very high HP, defense, and strength making him a very strong character. He will likely be the last man standing in any battle if things go wrong. By far the best all around attacker. Yang for his part in the game is the best damage dealer on your team. His elemental claws make it easier to target enemy weaknesses before you get Rydia back. His defenese is low but he has high HP to make up for it. Kick sucks for the most part but it is nice to have a free attack all ability.

I found Edge to be the least useful of the 'final five'. His HP and defense are too low for a front line member, and though his other abilities are cool, they are more like novelties. Blitz does come in handy sometimes but otherwise if he dies in a battle I don't have too much extra trouble winning most of the time. Just one less person to heal, really.