(For this post, I will be discussing polygamy, even though it would be more semantically accurate to say 'polygyny'. I know that etymology is against me, but I'm going to stick with cultural usage.)
It would be very easy for me to write about why I think polyamory is a better model for relationships than polygamy. I find the 'one penis policy' to be on shaky moral ground even when the women subjected to it are allowed to be involved with other women. Polygamy generally brings along with it judgemental attitude to sex outside of marriage, and regressive, restrictive gender roles. But there is a lot of criticism fired at polygamists that the polyamorists are attacked with too. And when you come down to it, we have a lot in common.
Yes, I know that polygamy has been used to oppress women, but so has monogamy, and I don't have a problem with people choosing that. In a patriarchal world where the men hold much of the power, just about anything can be used to oppress women (including polyandry, from what little I know of it). When it comes down to it, a polygamous marriage is just a relationship between one man and several women, and there are many polyamorists in that position.
Christine Brown, whose polygamous marriage was the centre of the reality TV show Sister Wives desired a husband with multiple wives so much that she actively sought the role of third wife. She wanted, what polyamorists can probably understand pretty well, to fall in love with a family, not just one person. Vicki Darger, when suffering from debilitating postnatal depression, found that being in a polygamous marriage meant that she had not just her husband, but her 'sister wives' to support her, and help with her other children. Speaking as a woman with two male partners, I'm obviously not going to want a relationship structure like Brown's or Darger's, but I can relate to the reasoning behind their choices.
Have you watched Big Love? I'm surprised at how many polyamorists haven't, and who assume that what polygamists do is very different to us. One scene in the first episode involves the three wives sitting down to organise their calendars, planning which night their shared husband will be spending with which wife and reorganising for birthdays. If you're polyamorous, you might be surprised at how much of their lives you recognise.
I was surprised at how much of it I actually envied. More than two parents for the children, regular family meals around an enormous dining table, shared finances, a communal back garden, and the ability to plan face to face, rather than just through Google Calendar. My husband and I talked about how although we were basically happy as a twosome, maybe someone or some people might come along that changed that. Maybe we'll have the chance to live more communally with secondary partner(s), or maybe one or both of us will find someone who wants to commit to our family as we have committed to each other. And despite being vocal about how my husband and I do practice hierarchical polyamory, it's been watching and reading about polygamy that's given me a less hierarchical model that I think would work for us.
Karaite Jews (for whom polygamy is rare, but permitted), some fundamentalist Mormons and Pakistani law all allow men to take a second wife, but only with the consent of the first wife. This effectively gives the first wife veto power, but not indiscriminately: you can demand that your husband breaks off his courtship of a potential new wife, but you can't demand that he break up with her once they are married. The characters in Big Love vote on whether or not to include a new wife. Although my husband and I have never felt the need to officially grant the other veto power, I would need him to consent if I wanted to bring anyone else into our family as a permanent spouse. A clear difference between our views and polygamous views on relationships is that we don't need marriage or co-primacy with our other relationships to consider them sucecssful, and we're not going to end them just because they aren't heading that way. But if our one of our other relationships did head that way, then that would be the end of hierarchy between the three of us. As Darger says about Val, the third wife in her family, once she was married to their husband, 'she instantly became a full and equal partner.' Equality between the wives is a common requirement in polygamous doctrines.
Perhaps this post doesn't make it sound this way, but I really am blissfully happy with one husband and one boyfriend, and so I'm not looking for either my husband or I to marry again, as much as I am attracted to larger family models. Even if I actively wanted it, it seems unlikely, considering how little space we have left for anyone new. But putting aside my feminist disapproval of polygamy to find out about those who actively chose it has been enlightening for me. I may be happy in my own form of non-monogamy, but other people's choices have a lot to teach me too.