The only similarity between these two families is the fact that they are both poor.
The difference is that the Cunninghams are proud people who do the very best they can where the Ewells do not really seem to care that they are poor and, perhaps, even revel in it.
Walter Cunningham comes to school in patched, but neat, clothes. He will not take charity.
Burris Ewell comes to school absolutely filthy. He is the dirties person Scout has ever seen and he has lice. When asked to go home and take care of these problems, he states that he is quitting school, having already "done his time."