It's one thing "knowing" it, it's another being able to "prove" it using stats and graphs
Glad you thought it was useful. Incidentally, it's no longer possible to do the kind of test which I put together, since Google no longer lets you run ads with 2 different domain names inside one Ad Group, so it's impossible to run a direct apples-to-apples comparison. I ran my test basically as long as I could, until Google implemented the change I just described...