Google maps download, maps.me or micro sd card in GPS for navigating?

I've taken advantage of this feature with Google Maps and with another app called Navigator that uses open-source maps.

What you get, if you download the maps ahead of time is this: the GPS will show you your current location on the generic map without using data (if you have data turned off).

That is incredibly useful. But, that is all it will do. If you are used to getting step-by-step directions--that needs data.

If you want to see what that is like, just turn off data on your phone and use the mapping apps to find your location.

I use the app "Co-Pilot" on my iPhone and it has worked well for me in the US and the U.K. This is not a free app, but once you download the maps for an area all you need is the gps. I don't think that maps.me does realtime routing.

Does Co-pilot use data though?

I use Here WeGo, which is a free alternative to paid apps such as Sygic and Copilot and works completely offline, provided you download the appropriate maps to your phone beforehand. They are the same company as Here/Navteq, one of the major global map providers, so the app's data is quite reliable.

For driving, I purchase maps on eBay for my GPS. My comment here:

https://community.ricksteves.com/travel-forum/transportation/garmin-gps-micro-sd-map-cards-for-portugal-and-morocco

For walking, I build custom offline maps with Maps.me. My comments here:

https://community.ricksteves.com/travel-forum/tech-tips/maps-me-is-a-great-offline-map-program-for-iphones-and-android

If you want to save money, download the maps ahead of time in Google Maps and then use that app offline. It will still give you turn-by-turn voice directions offline. It will even recalibrate offline if you make a wrong turn. I've done this in Ireland, England, and Belgium and it really works. Here's a link for how to do it:

https://support.google.com/maps/answer/6291838

Be sure to bring a phone mount for your car and a phone charger that fits into the cigarette lighter outlet--even though you are offline, it uses a lot of power.

I've used Co Pilot and Google Maps. In both cases, you need some data (or WiFi) to search for a destination but can then navigate using GPS and no data. If you miss a turn, it will redirect you without needing data.
Google Maps works but I like Co Pilot better because it gives speed limits, reads the directions much more clearly, and gives you alerts when you are going to fast or approaching a speed trap. It has lane recommendations, and count downs from 2 miles - more like a regular GPS than Google Maps.
As far as I know there was no cost for Google Maps. I paid $30 for Western European maps for Co Pilot. Co Pilot for US is free, so you can try it and see what you think. Turn the data off and see how it does without it. The Europe version is better than the US because it gives more information that isn't included in the US version. Download at home rather than when you're there.

For the amount of driving you have planned...take a GPS. You will be always be fooling around with the phone and maps and settings and besides, looking at the phone while you drive is awkward. The GPS doesn't need downloads for each country (and city if you want detail) and has a mounting for the car. If you rent a midsize car there is a good chance that it will come with a built in GPS at no extra charge (which I just experienced in Italy).

We're traveling in Germany right now. Using the GPS that came with the car. It's a Tom Tom . . . (the "chip" was missing from the car's built-in. The GPS usually works fine, but twice at night when I start to go somewhere there is no connection to the satellite. Also, the GPS didn't recognize the English name of a museum.

So, I used maps.me, and that worked perfectly! It got me to the museum, with voice instructions. It also got me back to the hotel. Really glad I have the maps.me, as they have helped when we are trying to find a place by walking.