Are women more sinful than men?
Yes, according to the writings of these two ancient men religious leaders.
King Solomon
Is purported to have had 700 wives and 300 concubines. I would assume he knew more than most men about the character of women. He conducted a test and this is what is recorded in the Bible of the results of his observations.
“Indeed, there is no one on earth who is righteous,
no one who does what is right and never sins.”
 “Look,” says the Teacher, “this is what I have discovered:
Adding one thing to another to discover the scheme of things—
while I was still searching
but not finding—
I found one upright man among a thousand,
but not one upright woman among them all.” (Ecclesiastes Chapter 7)
Mohammed
Had thirteen wives and was purported to had have a multitude of slaves and concubines.  I assume he too knew quite a bit about women.
The Quran records he had a revelation and this is what is written what he  observed about Hell.
      Narrated Usama:
The Prophet said, “I stood at the gate of Paradise and saw that the majority of the people who entered it were the poor, while the wealthy were stopped at the gate (for the accounts). But the companions of the Fire were ordered to be taken to the Fire. Then I stood at the gate of the Fire and saw that the majority of those who entered it were women.”
Who Was the Only Upright Man?
Solomon writings never identify who he decided to be the only upright man. Some may interpret him to be Job from the time of the patriarchs. Although Job was written in a later time after Solomon era, it could be the writer of Job either had knowledge handed down to him as were many religious beliefs beginning with Abraham. 
I interpret it to be another which I will reveal in my second novel on Solomon. In my first novel, As a Lily Among Thorns, I surmised the Queen of Sheba challange Solomon with this question.
“What do men really know about women?”
Are Woman More Sinful than Men?
The balance and true scales are Yahweh’s concern; all the weights in the bag are his affair. (Proverb 16:11)
Regards and goodwill blogging. 
Source Links
As a Lily Among Thorns HERE