I'm not sure yet which of the two builds to choose, and moreover I'm not even sure that there's room for a DPS Fighter without loosing the tank or another vital party member. But anyway, let's hypothetically imagine that there is, and that you with this party setup can get to level 100.
So far I've only tried the basics of each of the two builds, so I have no extensive knowledge about their effeciency in the end-game, however here's what I've observed so far.
Dual Wield: mainly based on low-damage fast attacks it's the pure damage dealer with no other purpose than to end lives. The lacks in crowd control (i.e. immobilize, taunting, fearing, stunning effects) are made up by the incredible amount of damage you're able to dish out. Without knowing I'm guessing if you go this build you're aiming towards Elemental Rage, or would you stick to Waves of Force? And more interestingly, if Whirling Wind is based on Normal Damage, as in the damage displayed on your character sheet, it would be seriuosly lethal for a DW setup.
Two-Hand Specialization: with high-damage slow attacks its obvious advantage is powers that does a percentage of weapon damage, such as Brutal Attack. But the choice of powers with this build is more of a dilemma: you have Brutal Attack for the sheer damage output, however it's single target damage and as such not the power that change the outcome of a battle as much as say Thunderous Shot would (Ranger power). Staggering Blow does no damage but is possibly the best crowd control power in the game, and not only immobilize loose mobs but prevent all incomming damage for up to 10 seconds in which time you can bring them down or at least get the situation under control. This power would only really shine though when encountering giant packs of mobs, and in those situations I'd prefer a power that kills mobs rather than control them, but I guess it's a matter of taste. The third power of choice is War Cry which I think is a highly underestimated power. For 20 seconds half your party (Ranger + Fighter, the ones doing physical damage) do +60% damage, and adding to that your Fighter goes berserk and crits for up to 15 hits in a row, which is a great focus fire ability (on bosses e.g.). And to top that, the rest of the mobs run around in fear greatly reducing incomming damage on your party.
On the basis of that I would say there's more variety in a Two-Hand build, and as such it could deal with different situations better, but as I said I have no extensive knowledge about that.
If anyone does, please share your point of view with us and if you can also include the talent setup you use.
Thanks in advance.