The arcade template will only let you put it under the navbar, which looks ugly if you already have an existing leaderboard in the navbar, or around the footer, which in my case is already a duplicate. Adding the adsense to the skin allows you to have a targetable ad for advertisers that only exists on the arcade page. It makes sense for my site, maybe others, maybe not everyone. If you take a look at my site you will see how it works for me. If it helps you too, then great!
-Raymond