I personally don't like intermixing Tracking Code (aka Campaign variable) with Marketing Channels as it may lead to incorrect insights. Additionally, both of them have their attribution windows. If I want to see how the overall Marketing Channel is working, I'll use the Marketing Channels that can be further broken down into the Marketing Channel Detail. If you want to adjust the rules, they'll need to done in the Marketing Channel Processing Rules. If you want to see how your campaign did regardless of the users subsequent channels, I would use the Tracking Code. If you want to see the visit level, there is additionally the 'Search Engines' dimension.