What the Rambam is describing is a healthy relationship, not an order of hegemony. They are both working together to form one coherent family unit.
Since this goes against the grain of the mainstream way of thinking, we'll need a bit of context. The Rambam quotes the Gemara in Kesuvos 67b that you must supply a poor person with his needs even when his particular need happens to be a certain extravagance that would be superfluous to you. And so, if he was once rich and got used to having runners ahead of him, now that he's poor, since he didn't get over that part you should supply that to him from charity.
We see from this not to look objectively at the material being suppled, but at the person's need. What is—or became—natural for him to desire, by withholding that you are taking away and hurting him. To stress this a drop more, you aren't holding back something extra; you are removing what belongs to him.
Now, with that out of the way, by the human species the male is dominant. He is structured and tempered that way. In a healthy relationship, the male acts as a male and the female acts as a female, in ways that complement each other. Being that it is inherent in his nature to be dominant and it is also natural for a female to appreciate having a steady pillar at the core of the household, it is therefore a great setup that she treats him as the head of the house in certain ways. (See Maharal, Nesivos Olam, Nesiv Ha'emunah, end of chapter 1.)
As for actual decision making, they are actually partners, obviously. The man is not "better". This is indeed a fine line to walk, but you can think of it as both working on the same script in which the man, or father, is the decision maker that decides with his wife. Dominant, but not superior. With the above reference in mind, he needs the position of authority, and she would be happy to defer that position in a healthy relationship.
I say this is a fine line because we have the Gemara in Bava Metzia 59 telling us how careful one must be not to offend his wife, and the Maharal in Nesivos Olam explains that this is applies particularly to a wife, since the husband is in charge while she isn't actually subservient to him. When he abuses his position to mistreat her, there is that added tension of an equally free person being subjected to his rule, which is made worse since the domination is not baseless.
This is already long winded, but you can see the Gemara in Bava Metzia 59a which discusses following the wife's advice. As you can see there, it is about the merit of doing so and on which topics, but not about who gets to disqualify the other's wishes.