Who shows more courage in the book and why?

I'd have to give that honor equally to both Mama and Ruth, but Ruth would come first. Her courage has no bounds. She's married, she works when she has to, she supports her husband, she buffers antagonism between family members, she genuinely cares for and tries to please her husband, and she is unselfish to the point where she'll do whatever is necessary to help the family attain their dreams.

Living with her inlaws isn't a picnic, but she dwells with them in peace, and she understands that their futures are co-mingled. She isn't afraid to voice her opinions to Walter and set him straight when necessary..... she allows him to be a man and gives him the guidance he needs. Her courage comes from her heart and the love she has for her family. There's no better kind.