Juana is a simple woman, devoted to her husband and child, and to what is expected of her as Kino's helper. She has the instinct to know when things are wrong or right, she has a very balanced mind, and her mindset is realistic. Her connection with nature includes her understanding of the powers of good and evil as part of human nature, which she fears and respects. She both prays and casts off evil spirits as her religion dictates, and she works through love and instinct. Sure, she has hopes and wishes for a better life, but this life she dreams of is not at all a fantasy. In her world, she does not dream: She plans.
Kino starts off looking quite similar to Juana. However, we realize that he is quite oppressed by the overlords. Being a man, he has a harder responsibility to provide for the family. Contrastingly to Juana, in his world, he does not plan: He dreams. When he finds the pearl, it consumed him. All the resentment he had felt against the establishment, all the pressure he felt from, those whom he had to serve, his own manliness, his role in the family, and his ambition were all affected by the greed of using the pearl and buy off his past, and re-create a future of riches and goods.
When Juana saw the effect of the pearl on Kino, she demanded that he got rid of the pearl. So much he changed, that the once loving husband actually hit Juana for even considering it. This is how they are the most different.