Esperanza and Nenny are two sisters in The House on Mango Street by Sandra Cisneros. The vignettes in the book are narrated by Esperanza, and each little scene involves Esperanza's observations about people and personal experiences in her neighborhood. Esperanza and Nenny appear to be not very far apart from one another in age since they play together with another pair of sisters in multiple chapters of the book. Esperanza describes differences between herself and Nenny in multiple vignettes, both in terms of each girl's appearance and in the way they think.
The first mention of their differences is in the vignette "Hairs". On page 6 Esperanza says that everybody in her family has different hair. Her own "is lazy" and "never obeys barrettes or bands", while Nenny's "is slippery-- slides out of your hand". Their hair looks different not only from one another's but everyone else's in the family too.
The second time she gives a comparative clue about herself and Nenny is in the vignette "Boys & Girls". On page 8 Esperanza says, "Nenny is too young to be my friend. She's just my sister and that was not my fault". She feels that Nenny is her responsibility as the younger sibling who comes right after Esperanza. Esperanza likens this relationship between them to herself being a "balloon tied to an anchor" (9). The implied message is that the age difference between them does make a difference to Esperanza.
The third instance of comparison is in the vignette "Laughter". On page 17 Esperanza's first statement is "Nenny and I don't look like sisters... not right away". Unlike their friends Rachel and Lucy who physically look related, Esperanza and Nenny do not share similar facial features. The ways that she and Nenny are the same is in how they laugh and certain other things Esperanza says she cannot explain. For instance, they both think of Mexico when they look at a certain house that reminds Esperanza of houses she had seen there in the past.
The fourth time Esperanza mentions a difference is in the vignette "Gil's Furniture Bought & Sold". She says that Nenny asks Gil a lot of questions, while Esperanza has only talked to him once during a purchase in his store. Esperanza refers to Nenny on page 20 as "Nenny, who is stupider" when she describes Nenny asking Gil how much the music box costs. Esperanza describes herself as being quieter and having to pretend she does not care about the music box, while "Nenny who thinks she is smart" talks freely with old Gil.
A fifth comment about their differences occurs in the vignette "Hips" on page 50. Esperanza feels superior to Nenny, Lucy, and Rachel because she knows some scientific things about what hips are for. When Nenny chimes in with what Ezperanza feels is an ignorant comment, Esperanza explains that Nenny thinks this way because of her age and makes the remark "She is stupid alright, but she is my sister". In spite of feeling like she is smarter than Nenny, Esperanza nevertheless feels protective of her and hopes that neither Lucy nor Rachel will point out that Nenny's comment was stupid.
The final example of Esperanza's distinction between herself and Nenny is on page 88 in the vignette "Beautiful & Cruel". Esperanza says that she herself is an ugly daughter that nobody comes for, but that Nenny has pretty eyes and optimism that she will get to pick and choose details about her future. "It's easy to talk that way if you are pretty," remarks Esperanza. Esperanza then resolves to grow up to be beautiful and cruel so that she too will have her own power and not have to give it away to the men she has driven crazy.
To summarize, the specific differences Esperanza points out between herself and Nenny are in their hair, faces, ages/maturity, intelligence, introversion vs. extroversion, and level of physical beauty. There are a fair number of ways she says they are also similar to one another. The differences mentioned show a gradual deepening of how Esperanza thinks about their relationship. At first her observations have to do mainly with appearances, then about responsibility and protectiveness for one's sibling. As times goes by, Esperanza expresses critical thoughts about her sister's shortcomings, and eventually a seemingly resolved sort of longing to be more like her sister as they both consider what the future will hold for them.