I would say that GrapheneOS is way better for advanced users than iPhone, but it is definitely vice versa for casual users.
Discussion
For the most part I use my phone for normy things, like waking up, scheduling calendar appointments, checking in to flights, navigation and photography. I find iOs to work *way* better for most of these. And because with Graphene you can (and should) turn off most of the Google stuff, you lose any potentially good UX that Android does have.