I notice that both characters' official backstory are under the influence of the Broken Inside archetype.
That contrasts slightly with their in-game manner: Auron's "are you going to sit here listening to her regrets?' and Lulu's "it's sad and pointless to think about it" (dwelling on past losses). I'm having trouble putting it into words, but in a way, I felt that these two characters differed from Wakka and Tidus in that they didn't angst so much about what couldn't be changed. Auron is very complicated, mind you; he certainly does show regrets in Zanarkand. Lulu takes a deep breath before they enter Ginnem's cave but finds that she is "getting used to goodbyes." She seems fairly unflappable-- "so together", as Rikku observes jealously.
One of my ongoing flaws as a writer is that I tend to put people in incredibly vulnerable situations and make them seem vulnerable and a little too fragile. It is a bad habit, allowing me to work out my own fears/issues in a sort of lab experiment, but I'm always concerned that I'm doing injustice to the characters. It's fun because it lets us have "hurt/comfort" scenes where we go "awwww" and mentally comfort these characters we like. And yet. It's... better as fanfiction than as canon. I'm doubtful about this official guidebook, which seems to emphasize their uncertainty, and makes their aura of authority and self-control out to be nothing but a false front, bravado. This is both intriguing and... disappointing, especially for Lulu. I complained about this on aulu. Why is it so hard for game designers and writers to have female characters who are strong-willed and/or sharp-tongued just because that is who they are?
If female characters are strong and sharp-tongued, designers seem to have to have it due to past trauma or some inner difficulty. Apparently it can't just be because they are self-confident and powerful. Furthermore, these traits, which are presented as endearing in characters like Cid (I'm thinking more VII than X) or Auron, tend to be "ice bitch" traits for women, a slightly negative trait. "Scaaary." "Grumpy."
I'm preaching to the crowd here, but gosh, isn't it ingrained? Lara Croft was the one exception, and then the film designers had to go and turn her into "daddy's girl" and make out that the whole reason that she's tough, independent, and cocky is because...er... she misses her daddy? That was very odd. :)
[[EDIT: Hmmmm. I may have argued this case too strongly. It is a nuanced issue. I like Lulu's slight vulnerability, and I really like the portrait of Auron as a tortured soul determined to win a battle he already lost. The Auron chapter is especially insightful. The Lulu chapter also confirms my suspicions that Lulu started her career as Guardian hoping to protect Yuna by getting another Summoner to Zanarkand first. That's neat. There are many things about this guide that are good. I just have mixed feelings about some of it. ]]