Here are the main reasons listed by Microsoft:
- A local account is created on the device and doesn't require Internet connectivity to sign in. It's independent of other services, and it's not connected to the cloud. Your settings, files, and applications are limited to that single device
- A Microsoft account, on the other hand, is associated to an email address and password that you use with Outlook.com, Hotmail, Office, OneDrive, Skype, Xbox, and Windows. When you sign in to your PC with a Microsoft account, you’re connected to a Microsoft cloud service, and your settings and files can sync across various devices. You can also use it to access other Microsoft services
It’s apparently not introducing the “benefits”.