YA Protagonists in Non-YA Fiction

At Original Content, Gail Gauthier has an excellent post about what separates YA from fiction written for adults with young protagonist. She compares two works with similar plots (blending families), one that's YA and one that was written for adult readers. Although the waters are still murky, one difference Gauthier finds is interesting:

"The YA book has a more positive outcome than the adult short story. That is expected of books for young people. YA is expected to have a climactic epiphany of new maturity, maturity, I'm assuming, being considered a positive thing…I didn't see anything positive there or anything that suggested that Joe [in the non-YA story] is more mature as a result of his experience, just far more troubled."

For the most part, I think the term YA could be exchanged with Bildungsroman, so I think Gauthier's point about the climatic epiphany of new maturity is a good one. I'd be curious to take a further look at adult literature with young adult narrators and see if they go the "coming of age" route as well or, as in Gauthier's test, look more toward a downward spiral.

Also, I think voice ends up playing a big part. Adult lit with a teen narrator tends to have more of a distance–it could be the narrator looking back, or it could just be more of an authorial view. YA tends to stick closer with the narrator and his/her current emotional turmoil.

How do you differentiate the two?