Consider has already taken the liberty of doing the math and theorycrafting for all 3 Dk DPS types. There are already EJ threads written up with all the details you could possibly want to know about spec, gearing, and particularly reforging.
Hopefully those guides will eliminate alot of the questions about what is best for each spec. I'll get links later if people are having a hard time finding them for some reason.
Also, as a summarizing point, all 3 specs (dw frost, 2h frost, and 2h UH) are within 2% DPS of eachother; the closest they have ever been. This is all assuming you're gemmed and reforged appropriately for your spec.