O'lan is my favorite character in this novel. She represents the place of women in traditional Chinese culture; she works like a slave, focuses on the promotion of her husband's place in society, sacrifices for her husband and her children, and places all of her loyalty within the boundaries of her marriage receiving nothing in return. As a wife, she is overlooked and taken for granted, but she is the glue that holds the family together; something her husband realizes far too late.
Lotus on the other hand, represents Wang Lung's success. He has achieved a staus (in large part due to O'lans actions), and can now choose a woman because he wants her. He can be frivolous because he already commands the respect of one who works.
These two women symbolize Wang Lung's financial evolution. As a poor man, he chooses a wife who will stand by him and contribute to the good of the family. Wealth allows him to choose Lotus for no other reason than desire. He wants her, and he can afford her.