I think we have all being going about this TWF vs S&B vs THF the wrong way.
Heroes are, by definition, exceptional individuals. Whatever your hero character specializes in, he will be amazing at it, no doubt about it. Because of this, it's useless to use arguments such as "Dual Wielding is ineffective because you have to be ambidextrous, nimble, agile, and super awesome in order to use it effectively!".
You're playing a hero character, if that's what it takes to be awesome at dual wielding, then he possesses those characteristics, at least if you're optimizing properly. The same thing applies to S&B and to THF.
No matter what conjectures we try to summon here, the fact of the matter is, there are very few historical accounts of dual wielding in actual battle, and even fewer historical accounts that describe in precise details a confrontation between two different styles, such as S&B vs THF or S&B vs TWF or any combination thereof.
Because of this, we can't really ascertain with precision the degree of effectiveness a given technique would have on those specific scenarios. Unfortunately, a two-handed swordsman wearing full-plate against a nimble Nitenryu samurai is something that will only happen in games or in our heads.
That's not even taking into account all the other fighting styles that were prevalent over the centuries. Like Spear + Shield, Long Spear, Polearm, only using a one-handed weapon with no shield...
In the end, in order to make a game enjoyable, all that really matters is that you try and find a balance between all the popular different fighting styles, so that no one style is strictly superior to the other - if only in order to accomodate several different players that want to each play a different kind of warrior without them feeling shunned by the other players decision.
In order to do that, sometimes, you just have to "go with the flow" and use movie/game logic. Like the fact that you can attack twice as much because you're using twice as many weapons. Or that using a sword with two hands equates to exactly 150% more power than using it only with one hand. Or that the hero that uses a polearm/spear is insanely proficient in it's use, but fails to grasp the SIMPLE concept of short hafting the reach weapon in order to hit enemies that are closer.
There's a hundred things wrong with D&D's combat system. Like the fact that combat is, quite frankly, static as hell. No real-world fighting, regardless of style, involves you staying still while your opponent attacks - and it's very difficult to imagine you dodging a full attack of 5+ attacks standing perfectly still inside your 5ft square without backstepping, sidestepping or pushing your opponent back as you parry.
So, basically, the TL;DR version is that we can all stay and circlejerk about it all we want, but in the end, no one has the end-all be-all of arguments for or against dual-wielding, or any one technique over the other. And if were still talking about fighting styles in game, it's pointless to argue about it unless you're looking to reinvent the wheel by designing a game from scratch that has an end-goal of being as realistic as possible... Which, probably wouldn't be any fun to play unless you had a computer assist you in all the calculations involved, or straight up turned all the ideas you had into a virtual simulation.