As someone who longboard commutes to school (~10-15 minute ride), let me offer my two cents. Longboards have bigger and softer wheels than a skateboard, allowing it to go much faster and further with less effort. Also, the bigger length gives you a solid foundation on which to stand on.
If you've never longboarded before, you'd be surprised how maneuverable the things are. If you're imagining a skateboard trying to turn then you have the wrong idea.
In the end, the debate between a longer vs smaller longboard for commuting is up for debate. A longer one allows you to have bigger wheels, which increases speed and minimizes effort, as I mentioned. But a smaller one gets you some convenience in portability. In the end a longboard gets you somewhere in between a skateboard and a bike in terms of speed and effort.
