Given the choice, what are the pros/cons of mixed-mode assemblies vs. separate interop DLLs?

The title says it all really.

When a 3rd-party component is offered in both "mixed-mode assembly" and "separate interop dll" versions, what are the pros and cons of each?

A good example is System.Data.SQLite.

The above link has this to say:

[mixed-mode assembly] packages should only be used in cases where the assembly binary must be deployed to the Global Assembly Cache for some reason.

But WHY? The mixed-mode assembly seems to work just fine in my projects, with no GAC installation (just xcopy to the application's exe directory). It's nice to have one less DLL. It feels tidier. So what are the cons?

Vice-versa, why would/should one ever favor the two-DLL "native-dll + interop-dll" version?