Broken Dragon is worth a read. Firelight should be avoided at all costs.
As the other reviewer has noted, Broken Dragon has a few flaws when it comes to characterization, like Zuko being willing to torture Mai because he thought she might have betrayed him, but on the whole those flaws weren't game breaking. It's a solid Ty Zula fic that doesn't completely gloss over Azula's metal health issues. There's a solid character arc for Azula that's interesting and presents a sort of non-redemption redemption story. The relationship between the three Dangerous Ladies is also good. The sequel, however, is pretty much bullshit. Mai and Zuko become designated villains. Azula and Ty Lee can do little wrong. Their domestic life in Ba Sing Se is an interesting story, with well-realized O Cs, that gets discarded once Azula is pulled back to the Fire Nation. And the ending... ugh. Zuko is killed and his friends are just pretty okay with it.
Good fic, terrible sequel.
Broken Dragon, in spite of being listed as a shipping fic, is actually a very neatly written character driven story about Ty Lee and Azula that manages to remain interesting and capturing in spite of some very glaring flaws. Throughout the fic we see some severe Character Derailment, most glaringly from Zuko (who turns from a reasonably scared and understandably bitter brother, to a heartless asshole in a moment's notice) , Mai (who's entirely too supportive of said asshole), and Toph. But the author manages to save it by carefully nurturing and raising his main characters throughout it, creating a consistent and decidedly interesting character arc for Azula while remaining true to the protagonists canon personalities, and presenting the development of their relationship in a well thought out and sensible manner. All while maintaining a decidedly neat style. Every aspect of it, from the initial set up to the climax and resolution remains interesting, and the story is resolved in a rather satisfactory manner. It is sad that Firelight could not follow on it's predecessors footsteps. While the author retains a fairly neat writing style, the story arc itself seems to take back seat to Azula and Ty Lee's already pretty much set in stone relationship, which quickly makes it devolve into a fluff fest that may as well have come from the pen of Stephanie Meyer. All previously established character growth and development for any plot relevant characters, be it on the previous instalment or on canon, was forgotten, once against the most obvious victim being Zuko. While others were overstated to levels that basically killed all Willing Suspension Of Disbelief, the most obvious example being the aggrandizing of Azula from a self serving conniving criminal driven by deep seated daddy issues, into a righteous ruler, in less than 2 months time. Not to mention that the fic opens up with about 10 chapters of plot about Azula's and Ty Lee's life on a Ba Sing Se (even introducing genuinely interesting original characters) that become completely irrelevant shortly afterwards. That and the constant overplaying of Ty Lee's innocence which eventually starts bordering on stupidity, have made the whole fic unbearable. My advice to you is to read the first fic, then just assume a Happily Ever After.