To make objects linkable : group or collection?


in Blender 2.79, objects have to be in groups to be linked properly. It’s the same in Blender 2.8 but we have the choice between : Move to Collection" (M) -> “+ New Collection”, or “Create New Collection” (CTRL + G). The difference is that with “CTRL +G”, we don’t see that the object is in a collection (as group in Blender 2.79).

What is the best way to make objects linkable in 2.8 please ?