Why does it seem that there are more difficult mother's than difficult fathers?

Main difference is the number of women who survive to advanced age vs the number of men. A very small percentage of a much larger number becomes much larger. Another factor is that women do the largest portion of caregiving and they can have difficult relationships with their mothers and mothers-in-law. My mom is practically a living saint, but it still gets difficult because of the constant demands. It's mostly grief and anger over what's been lost.

Women outlive men so there are more of them that make it to the stage of needing care. Plus often difficult women are counterbalanced by their spouse and once widowed they have no one to keep them in check. I also think that women of the oldest generation now needing care were more accustomed to many aspects of their lives being taken care of by someone else, and rather than developing independence after being widowed they turn to their children to pick up that role.

My husband and I always said we hoped my father would die first because my mother would have been so very appreciative of everything done for her as she aged. Unfortunately, my mother died over 20 years ago and my father is 102 and still making our lives miserable.

My mother would have been a joy to care for. Not my father, he wanted to be babied and catered to.

Hormones, women are more emotional and express this on a too regular basis.

Many men entitle the woman to get her to calm down so they can have some peace, that also causes women who cannot do anything for themselves. Then they become helpless and needy, and then get upset when their needs are no longer met.

Just my 2 cents of course!

No matter our current intent to prove that there's no difference between men and women, there are in fact MANY differences. I love listening to Dr. Laura Schlessinger. She claims "men are easy". She says you just need to use a little love, a simple apology and they are ready to move on. Just a "Honey, I am sorry; I love you. You're so good to me" and they are good to go. But women are on and on and on about things with "nah-nah-nah-nah-nah". I think it's true. Men are of a "fix it" mentality. They like things smooth and quiet. Women are wanting always to regurgitate and ruminate loudly and continuously.
I speak now in generalities. We do have those women who disengage and go about their business peacefully and we do have those men who whine on and on. But generally I think the templates are different.