When I walk in the mountains here I am walking in a big empty green square according to Google :S Same with Apple.
Meanwhile OSM knows every little trail including surface and gradients <3 It's amazing. And I can turn on layers so I only se the things I need and not everything else.
And not just there, also when walking in the city. Little shortcuts are often not on Google maps at all. The only thing where I see Google beat it is live public transport information.
And perhaps traffic but I don't drive so I don't know how good that is.