Question about the relationship between a weapon's req and attributes.

I've heard from someone that the greater the difference between your attribute and the weapon's req, the higher chance you'll have for critical attacks, and higher damage.

Example:
I have 2 Max Wingblade Swords with Damage +14% while above 50% health. One is req. 12 Swordsmanship and the other is req. 9 Swordsmanship.

If I used a Superior Swordsmanship Rune, would I do more damage with the sword that only has req 9? Or would it be the same as the sword with req 12?

Swordsmanship by itself increases critical hit rate, so just having 16 swordsmanship as opposed to 12 will give you more critical hits. However, I don't think that having higher swordsmanship over the weapon requirement gives you more critical hits.

The weapon requirement has nothing to do with damage, criticals etc so long as you are at or over the requirement.