Like Tesla's existing hardwired option, the advantage with the new device is that it lets you keep the mobile connector in your car for use when travelling. What's unique here is the attached NEMA 14-50 plug, allowing users to take the wall connector with them if they move.
Tesla claims that it also has the benefit of not requiring an electrician installation -- "simply mount [it]...to a wall...and plug in" -- but (as Electrek notes) that only works if you already have a NEMA 14-50 power outlet. And, if that's the case, then you can just revert to using the Mobile Connector anyway. At $500, the new charger costs the same as the hardwired version and is available now on Tesla's website.