There is also a large amount of crossover as embedded gains more resources. Often you're working with javascript because your device needs to have an embedded web server with custom functionality. Sometimes you see SQlite on embedded flash, although debatable if they really needed it. Running Linux is far more common and it works pretty much the same regardless if it's on an MCU or a VM in the cloud.
The main difference I see is to do with the ease of fixing mistakes in the field. With web development I can usually git push and the issue is fixed for all users. With embedded, I almost never have an internet connection so it's a case of physically sending people to site or product recall to fix the issue if it's serious. Internet connections are becoming more common in embedded so we can remote update, but still the minority in general.
Lots of common ground, but just like any discipline it's that last 20% that makes the difference.