Feminist scholars have divided Disney heroines into four groups: The Classics, The Good Daughters, The Princesses, and The Tough Girls. I'm going to tackle each group one at a time, and it's only fair to start with the ones who started it all: Snow White, Cinderella, and Aurora.
The original princesses have very similar personalities and traits. They are all kindhearted, innocent, beautiful, asexual, goodnatured, and musical, and two of them (Snow White and Cinderella) are used to forced physical labor. (We can probably assume that Aurora has seen her share of labor because of her peasant life, but not because of cruelty towards her.) Also, all three princesses lack a decent mother figure; Cinderella and Snow White suffer from cruel stepmothers, and while Aurora has a biological mother, her mother is unable to protect her and she spends 99% of the movie unaware of her mother's existence. The evil woman who is after them is conniving, intelligent, calculating, and often hates the heroine purely because she is innocent and beautiful, while the villainess is depicted as over-sexualized and evil on all accounts. So Walt's original creations all have very similar stories, but they have personalities of their own that are worth exploring.
Snow White, the original and the standard, often takes considerable flak for her cutesy, naive innocence, and some of that flak is deserved. From the first sentence she utters, Snow White wants nothing more than for her prince to come. She has no interests outside of finding him, no hobbies outside of being with him, and no goals other than marrying him. When the witch comes along and tells her to make a wish, any wish at all, Snow White asks for a prince. She doesn't mention the fact that her birthright has been taken from her by force, she doesn't fear that her kingdom is being ruled by an attempted-murderess, and she doesn't even wish for her position back. She just wants the Prince. Everything else can come as it may, but as long as she has a boyfriend, everything will be alright.
Snow White doesn't make things happen; she reacts to things that happen to her. The most active part she takes in her own life consists of setting up housekeeping with the dwarves, which she did more or less by force (since she quite literally barged into their home.) However, she's not content to be taken care of. She works and cleans and maintains order, becoming the "mother" of the group. It even seems that the dwarves need her, although they didn't know it until she informed them of it. However, her trusting nature and naivete keep her from being much use; as soon as the dwarves are gone, she bites the apple and nearly dies because she ignored their warning.
Snow White falls into two basic categories of female stereotypes portrayed in film: the Contented Homemaker and the Innocent Ingenue. For one thing, she is naive and trusting and seems content to remain so; the fact that she is childish and completely unsexualized are her redeeming features and set her aside from the conniving, vain queen (whom, we are lead to assume, is jealous of the Prince's advances on Snow White.) In the Contented Homemaker, she merely needs someone to take care of. She comes upon the dwarves and completely rearranges their lives. There isn't anything innately wrong with the way they are living, and they seemed content without her, but, as a true mother-figure will do, Snow White sweeps in, takes over, and becomes the mother they didn't know they were missing.
Cinderella shares many of Snow White's traits, but has a different personality. First of all, we are lead to believe that Cinderella is a grown woman, at least 18 or so, and so she lacks the childish whimsy of Snow White. Also, she has a refined elegance and grace about her that was highly admired in women in the 1950s, a time period when domestic bliss amongst women was the top priority. She is lovely, gracious, and always keeps a smile in her heart, no matter the circumstances. She seems to accept her lot in life with a good level of equanimity. In the beginning she talks of dreams being her one rebellion, but she never mentions exactly what it is she wants. We are lead to believe she's dreaming of a husband, but she doesn't ever tell us; for all we know, she could have been dreaming of going backpacking around the rainforest. (This vague "dream" will come up again with a vengeance later on.)
Having accepted her lot in life, Cinderella shuffles through her daily existence without ever losing her quiet dignity, until the day comes when doing what she's told will no longer do. When she first attempts to go to the ball, she tries to do so with her stepmother's permission. Sneaking off to the ball was never in the original plan; she intended to attend with her family. However, after her stepmother gets her hopes up and than crushes that dream, Cinderella is faced with a crucial decision: slink back to the attic and accept her fate, or take the opportunity to go to the ball anyway (with some help from the fairy godmother, of course.) It is in choosing to go to the ball anyway that Cinderella departs from meek, submissive Snow White and becomes a pale shadow of a modern heroine, a preliminary sketch of what was to come.
Of course, once at the ball, she falls in instantaneous love with the prince and is later swept off her feet, and we are lead to believe that she and the Prince rush off into matrimonial bliss after that, but let's not downplay the significance of going to the ball anyway. By attending the ball, Cinderella risked public humiliation or worse, depending on her stepmother's rage, so going was no simple decision. Cinderella is living proof that you can only push even the BEST of women so far, and for that reason, Cinderella was an enormous step forward as far as feminism for Disney animated heroines. Unfortunately, the next Princess would ultimately be a large step BACK....
Aurora was released to the world less than 10 years after Cinderella was, and there could not be a bigger difference between the two. Of course, they share the same traits as Snow White in several ways, but while Cinderella ultimately took some initiative, Aurora never does. Throughout her sparse 18 minutes of screentime, Aurora doesn't take one active step in her own life. She sings, daydreams, dances with a strange man, is lead around by others, sleeps, and than dances with the strange man again. Even when she is given the simple task of picking berries, she doesn't really do it, she just picks a few and than frolics in the woods.
However, Aurora does have one redeeming feature that I bet you've never thought of: she is the first princess to be forwardly flirty with a man. If you recall, Snow White runs away from her prince, Cinderella just seems starstruck by hers (and eventually runs from him,) but Aurora pantomimes being flirtatious and almost sexy with her pseudo-prince, the Owl. When he is dressed in the Prince's robes, she saunters up to him, dances against him (pretty suggestively for the time period), and flirts pretty aggressively. Of course, as soon as the real prince shows up, she dissolves into a shy, awkward, inert lump, but still, it's a pretty big step. The Classic princesses are portrayed as good because they are entirely innocent and completely unsexualized, so the fact that Aurora was flirting pretty forwardly, if only in her daydreams, is a pretty big accomplishment.
I hope you've enjoyed part one! Be looking out for Part 2: The Princesses. :)