Good for you one mega-city in Europe* got proper apple treatment after 10 years lets wait 20 more years for other monster cities, and then they can maybe add some cities under a 10 million population :D
I’ve used Google Maps’ offline saving feature when traveling internationally and where cell service is poor or absent.
I should mention that Apple Maps, being vector based, can be pre-downloaded using the hotel wifi when you are in a roaming area and will work for many blocks around the hotel without using the radios. Google won’t.
You download a region before being there, then you can use the app completely offline. The 'completely offline' modus only works for the downloaded data, obviously.
I'm using it quite a bit abroad, since roaming data outside of Switzerland is really expensive :)