NT Authority\Authenticated Users vs All Authenticated Users

What is the difference between All Authenticated Users and NT Authority\authenticated users?

We have a 2010 SP1 Enterprise Farm - new install not upgrade, multiple web apps, mixed authentication models, Claims and Windows.

The Site Collections in the Claims based web apps, allow me to add both All Authenticated Users and NT Authority\authenticated users. However, the Windows based Web Apps will only allow me to select All Authenticated Users. - I assume NT Authority\Authenticated Users is only available to Claims based Web Apps.

Q3.) Which should I use in the claims web apps, All Authenticated Users or NT Authority? (I assume I must use All Authencticated Users in Windows Authenticated Web Apps, since I do not see NT Authority\authenticated users (the people picker looks different as well))

There is one rather telling distinction when assigning permissions. With claims-based authentication, All Authenticated Users implicitly includes any claims providers that the SharePoint STS trusts. The scope of NT AUTHORITY\Authenticated Users scope, by contrast, a la SID, is the AD domain.