Hi Rob.

The Declink standard only gives you SDI, but it works. Blackmagic has a problem with interference in their monster cables for the Extreme and Pro cards, when using long SDI runs. Miglia card works well.
If you invest in both cards (wich is cheaper than the extreme) you have the option of switching between them in Catalyst. You cannot use more than one input at the time on the Decklink Extreme.
Our machines have both and we are happy!