Port-ability. ;)
Seriously though, Switch is more of a powerful handheld with additional functionality that makes it home console as well (Nintendo did a great job marketing it other way around, so they can sell games for $60 instead of $40) - so really there's no mystery why it's selling as good as it does.
As much as I'm not too keen on actual execution, I think it's very good concept for people who care about portability.







