I think one of the biggest mistakes floating around is the idea that women actually have a preference at all.
I often come up with simple analogies to explain the nature of women (or at least the nature of women as I see it), and when it comes to discussions of nice guy vs. jerk (or any variation of it.... well grounded man vs. douchebag, in this case), I like to use this particular analogy of a solid rock protruding from the sea.
In this analogy, the ocean represents the jerk. It is dynamic in motion. Its turbulence creates the sounds of crashing waves that elicit emotion. It offers the allure of exploration and a mystery as to what might be found out there. It calls for a woman to explore it.
The rock is the well grounded man. Solid. Immovable. Dependable. A safe haven one can cling to for life when necessary.
Sometimes you will come across a woman when she is sitting on the rock. Meditating. Enjoying the comfort of peace and safety that the rock offers. But sooner or later the rock becomes stale and the mystery of the sea will call her to explore it. These are the women who end up cheating on their nice guy boyfriends, wives cheating on husbands and such.
And then sometimes when you come across a woman, she will already be out at sea. She is enjoying the adventure. But sometimes a storm rolls in, those seas get violent, and that sense of adventure turns to fear and self preservation. She begins to panic and seeks out the safety to which that solid rock offers. This is a woman who is dating a douchebag and complains she can't find a nice guy. You may notice a woman will always say this, not when the seas are more manageable and inviting, but at the height of the storm.
Many men would describe themselves as being either the rock or the ocean, and these men will believe they are constantly dealing with two types of women, each of which have a preference.
What few men realize is that the woman on the rock and the woman at sea are one and the same person.
Women need contrast. They need both. And they seek a man who is the perfect embodiment of both: Strong, solid, dependable, immovable, safe, but also provides a sense of adventure, mystery, a little danger and the allure of exploration. And because few men are capable of being both, a woman must often chose one against the other. It is not a preference but a forced choice. Sometimes she will bounce back and forth between the two in order to fulfill and satisfy her need for both qualities.
No woman wants to stay on the rock forever.
No woman wants to stay out at sea forever.
The more a man can be of both worlds, the more he will own any woman who steps into it, the more she will surrender herself to him and the more she will act to preserve what is perceived as so rare.