I would have to say my wife and I are both a bit of size queens. As many of our friends are in the lifestyle (nice word for swingers) we both agree that most of the women in open relationships are to some degree after a big dick. For a smaller group of them the bigger the better. For most it seems like they have "perfect size" in mind, and its above average for sure.
As a bi guy I tend to hang out with other bi guys and, at least with my group, it seems to be much like the women. In my experience, and its not extensive, with guy men. It seem they have a larger group of men with the bigger is better additude. I don't thing it is all of them but in percentage VS the woman it seems to be higher.
Understand all if this is subjective based on my experiences. (your mileage may vary)