who is more affected by their surroundings, scout or jem ? and examples of how?

I think that Jem was coming of age and begins to understand the ugliness of the world. Scout too is affected by the situations but manages to retain a sense of innocence. Note Jem's reaction when Tom Robinson is convicted for the crime against Mayella Ewell,

It was Jem's turn to cry. His face was streaked with angry tears as we made our way through the cheerful crowd. "It ain't right," he muttered...
"It ain't right, Atticus," said Jem.
"No son, it's not right."