I'm looking at a few of the samples.
There are some GraphicsOverlayexamples
These create points, lines and polygons for display on the screen.
Presumably, the data just in memory.
There is another example called CreateFeatureCollectionLayer.
This creates points, lines, and polygons for display on the screen.
While there are many ways to create FeatureCollection, this example creates it from scratch and puts data in it.
The data is just . . . well, I don't know if it is just in memory.
But if it does make it to persistent storage, I don't how you would get it back later.
I see there are methods to save it to a portal item. Not sure that would apply to Basic licensing. Nothing to save it locally, though.
So, if they are both in memory objects, why would I use one vs the other?