You can use google maps without using any data, theres an option that allows you to download a section of a map u require. Its called offline maps.
Sounds stupid, but I didnt even know you could use google maps to navigate with. Still always going to be a Tomtom user though - much prefer the bigger display & its far better than the one built into the car. Saying that, I bet Google would be better at Voice Recognition than the others :/ https://www.youtube.com/watch?v=kupwNuOGmvg
Google maps is using ridiculously small amount of data I presume other apps are similar.
I use a tom-tom because I don't have unlimited data on my phone. I bought it around ten years ago though. Does the phone app work without Internet data?
I like your justification