I have talked with several Christians about marriage and the Bible. We ended up talking about gay marriage, Biblical view on marriage and how husbands should treat their wives.
The obvious gay marriage tends to come up, but it is dealt with in a weird way. The Old Testament says to kill them. The New Testament is against it (depending on how you interpret Paul's words). However, there is nothing about gay marriage. The choices seem to be to follow the OT and kill gay people or maybe ignore that and try not to be gay. But it doesn't say anything about how how civil unions are ok while marriage is not. That stuff pretty much just comes out of preacher's biases.
There is a lot of talk about how God wants marriage. However, if you look up how it was originally set up in the Old Testament, a marriage is a man, one or more wives and his concubines and slaves. There are many passages supporting this and many times God blesses such a marriage (like Jacob's or David's). The Biblical view of marriage also had rules like making a raped woman marry her rapist and killing women who are not virgins on their wedding night in front of her parents. As a society we have rejected these things as bad morality even though it is promoted as good in the Bible. But many Christians tend to be in some weird middle ground where such things are just ignored and pretend the Bible only teaches virtues.
Finally, we talked about how a husband treats his wife. This got caught up in how a master treats his slaves. The spin was the same. The husband/wife is equal before God in some spiritual sense. The husband is the head of the house but the woman is equally important in maintaining the household.
However, in the discussion on slavery in which the Christians were trying to justify why slavery was acceptable in the Old Testament, they said that the master/save relationship forms one in which they are equally important before God. The master makes the decisions and the slave carries them out. But they are both equal before God.
So what I took away from this is that it is very easy to rule a wife but spin it as she is equal. Personally, let people fall into the relationship they want. If the woman is better at making decisions, then let her. If they like to share in responsibility, then work on that model. A penis or vagina doesn't make a compelling reason on why one partner should be subjugated to the other.