The primary advantages to the Ibo family structure lie in the communal nature of the society. Children are raised by all wives, which may take some pressure off each mother individually. Also, all chores are shared amongst the wives and children-so again, there's much less stress laid upon one person. Furthermore, the children benefit from the "village" raising them-bonds within the community are closer, and the idea of an extended family atmosphere offers opportunities for relationships that might not otherwise develop. As far as the relationship between husband and wives, the fact that they have their own huts may be an advantage, as everyone needs their own space to return to at the end of the day.
Disadvantages to the Ibo structure would have to be looked at through an American perspective of family values. Most families are nuclear, which accounts for strong relationships that may be lacking in Ibo culture. Of course, most Americans would balk at the idea of polygamy. Having to share your husband with more women, or having to look after others' children would not sit well with many American women. In addition, many would consider it a sin. Indeed, the Ibo female roles would probably anger many women. American women take control of their careers, as well as their families, and the very strict gender roles of the Ibo do not allow for such freedoms. Women are responsible for the home, the children, and certain crops. They do not have the rights of American women.
As listed above, advantages to the American family structure would be closer relationships between spouses and parents/children. There would also be less distribution of resources for most families, leading to greater prosperity. There would be fewer opportunities for jealousy or rivalries between siblings and spouses as well. Again, the role of women in America is much freer and open than the restrictiveness of Ibo society. Disadvantages would include lack of community support. If your family treats you poorly, you'll essentially have nowhere to turn. Also, children may miss out on chances to develop relationships with many siblings.