[c#] What's the difference setting Embed Interop Types true and false in Visual Studio?

This option was introduced in order to remove the need to deploy very large PIAs (Primary Interop Assemblies) for interop.

It simply embeds the managed bridging code used that allows you to talk to unmanaged assemblies, but instead of embedding it all it only creates the stuff you actually use in code.

Read more in Scott Hanselman's blog post about it and other VS improvements here.

As for whether it is advised or not, I'm not sure as I don't need to use this feature. A quick web search yields a few leads:

The only risk of turning them all to false is more deployment concerns with PIA files and a larger deployment if some of those files are large.