Blocking shots is strong defence. Not everybody can be a puck possession player, which by its very nature is an offensive stat. You need players who know how to stop the puck from going in the net, and for years Gorges has been among the best in the entire NHL at this. Taking away shots on goal is an extremely valuable skillset.
If you look at the numbers over his career, its a fair argument that Gorges tended to supress the amounts of shots against his net while playing hard minutes, with the a significant part of that being the number of shots he successfully blocked. Similarly he had a strong track record of success as a penalty killer by any metric. You can't say the same thing about Emelin.
Now, its reasonable to say that Gorges was heading into a predictable decline and the Habs were right to get rid of his contract. But if we're talking about how they played in a Habs uniform, Gorges was the superior option to Emelin and Gilbert due to his value as a defensive specialist who could play significant minutes in a supporting role.
