While both women are constantly seeking relationships, Leslie's relationships don't conflict with her self-esteem. In fact, all of the men Leslie dates either end up dumped on the side of the road or rejected because she recognizes herself as a worthwhile woman. Ann, on the other hand, consistently changes her personality to match her current boyfriend's, as is demonstrated in the clip below.
Eventually, however, Ann finally comes to terms with her predisposition to change depending on her love life, stops dating, and decides she wants to have a baby. While this change might present Ann's transformation to a preferred character, Ann's struggle to find a sperm donor is lengthy and difficult due to the need of a man to produce the sperm. Thus, throughout the series, Ann is unable to achieve her desires without the help of a man.
Leslie, despite her lack of successful relationships, constantly sticks up for herself, as is demonstrated in this clip.
While Leslie being saved by Ben could be considered a preferred event during the series, this is the only event in the series in which Leslie isn't able to save herself from her mistakes. Obviously a more in-depth study of the series could argue that this is an occluded preferred reading, but a deeper analysis of Leslie Knope's relationships bears further study.
Do you think Leslie is an oppositional character or a preferred character? Why?
How would you analyze Parks & Rec in a pop culture analysis?