The offense would definitely have been different with Cook. He's a much more explosive player than Murray or McKinnon, so I think he would have definitely had a few more long TD runs. Before he got hurt, I was worried that they were overusing him, so we likely wouldn't have seen Murray and/or McKinnon establish themselves like they did. Maybe that doesn't matter, but I do think that Murray's physical running has been a big part of our success.
I also think that if Cook is healthy, then the running game would be more to the outside/horizontal. They've tried doing that some with the other backs, but Murray is a north-south runner and while McKinnon can hit the edge, they don't do it a lot with him. I also really would have liked to see how Cook developed in the passing game. Had some trouble catching the ball early, but he really stepped up in pass protection.
We've gotten what we needed out of the running game, but another explosive dimension to the offense would be really nice.