I'm not great at number crunching, but looking through the strategy guide, it seems to me that 2-Handed Weapons would be more powerful than Dual Wielding. Now, that's not supposed to be the case, so I am assuming that I am not considering all of the information.
According to the Skyrim strategy guide, equivelent weapons (I.E.: Steel Sword v. Steel Greatsword), the damage output seems to favor the 2-Handed Weapon by double, sometimes more. For instance, a Steel Sword does 8 damage, while a Steel Greatsword does 17 damage, which is double +1.
So, the way I see it, if I were to have 2 Steel Swords, that'd be 16 damage per swipe, as opposed to 17 damage per with the Steel Greatswords.
Now, obviously the Steel Swords are lighter - so is that where the difference comes in to play, that even when dual wielding, the 2 Steel Swords will attack faster, thus dishing out more damage? I'm not sure how exactly the attack speed of a weapon is calculated, I only know that the heavier the weapon, the slower it is, but not necessarily to what degree. I.E. the Steel Swords have a weight of 10, where the Steel Greatsword has a weight of 17, so I don't know how those stats translate to in game effect.
So... what is it that I am missing here in the calculations regarding Dual Wielding vs. 2-Handed Weapons? I just did a little practice run through to test some things, and this was the first time I've ever used 2-Handed Weapons, and I felt more powerful with the Greatsword as opposed to the Dual Wield swords I typically use. But perhaps that has to do with buffing all my points into Health, to more properly "tank" and sit there and take blows, when typically I am dividing my points between Magicka and Health, something I would be doing with my official build.