Sabriel has few characters, some of them introduced well after the story begins like Touchstone. The plot is about this healthy, strong girl with an okay life save for the fact that she battles the Dead. But she goes to a magic school, so battling Dead is only mildly weird.
Lirael, on the other hand, starts at home, in a big Glacier with a lot of people. The character is a girl that doesn't belong. She finds out she's this Chosen One, and goes through an epic adventure to uncover who she is. It sounds like a meatier, more envolving premise in general for a big screen.
Don't get me wrong - I loved Sabriel best out of the three books because it was no-nonsense, let's get this party started kind of messy fantasy. Sabriel as a character was awesome, scared as hell but toughing it out without feeling too sorry for herself. The dynamic of Sabriel and Co. was cool, too.
I'm just intrigued at how Sabriel's composition could change the pacing of a possible movie. I feel Sabriel would be more of a Stardust [action now, think later] movie while Lirael would be a more LOTR [big themes, big ponderings] movie. Or maybe a Sabriel movie will put an experimental spin on the fantasy formula. What do you guys think?