I'd say the choice of DX or D1 depends on how far away the last slot is from the video card. Since my motherboard places PCI slots farther away than PCIe slots, I bought the D1. The farther away it is, the less EMI it will absorb from the video card. Or so I think. The DX requires a power cable whereas the D1 does not.
There are some people who say that taking the DX over the D1 is more future proof. Whether or not this is true is kind of debatable.
I'll go for the DX, thanks RallyMaster and all the others for your support