The main difference seems to be that today even getting the top organic search result doesn't provide enough clicks for advertisers, so they feel obliged to purchase ads for their own brand names even when they already rank first.
It should be noted that this instance is simply a test and should not be taken as an indication of how these ads will be purchased. While I'm sure there will be numerous advertisers who feel the need to have a large banner when their specific brand is searched for, I expect them to be in the minority. The real question is will I be seeing a banner for Southwest when I search for JetBlue.