Okonkwo worries that from an early age Nwoye seems to be more like Okonkwo's father than himself. So he worries about him being weak and womanly and not interested in working hard and becoming a great wrestler and warrior, all the things that Okonkwo thinks are most important in life. Because of this, Okonkwo is frequently angry with the boy and wishes he was more like Ikemefuna, the boy given to Okonkwo from a neighboring village. Eventually, during Okonkwo's absence from Umuofia, Nwoye converts to Christianity which further enrages Okonkwo.
Ezinma, on the other hand, is a girl Okonkwo wishes were a boy because she has all the traits he loves. She is smart, hard-working, and tough in all the ways that Nwoye is not. So Okonkwo favors her despite the fact that he knows she cannot succeed him in the way a son could. Of course, even with Ezinma, his affection is only rarely demonstrated.