Windows 10 suggests that you use a PIN to login to your computer and says that this is more secure than a password.
These seems odd because obviously there are fewer possible values. This article explains the reasoning about PINs.
In short, your Microsoft Account credentials are the crown jewels that you want to protect. They provide access to the ability to spend money and configure email etc.
The PIN is device specific, therefore if it is lost you are only giving away access to that device not your account. Crucially if you login with the PIN you will be prompted for your account password if you want to do higher privilege operations such as spending money.
If your PIN is compromised you can go to your account and reset it.
In summary, the additional security of PINs is welcome and you should always use a Windows 10 PIN with your personal computers.