Probleme about grapheneOS is it only supports newest Pixel phones. They recommend a minimum of Pixel 6 which most people can't afford, even in the second hand market unless they have a broken screen or are in a sorry state while I can get a Samsung Galaxy S9+ in very good shape for the price of a new entry level smartphone and install it with /e/, iodé or divestOS.
So I would say they are not targetting the same users and you can't really compare them equally.