I'm unfamiliar with maps.me or organicmaps -- what's the value prop versus just downloading a region from the Google Maps app? Is it opting out of big tech? Or is there some other capability that doesn't exist in Google/Apple's apps?
1. Freedom. When using Organic Maps, you have the right to use the app in any way you choose; this includes the right to modify and redistribute the app should the developers ever start violating your principles. In fact this is exactly what Organic Maps is. Before Organic Maps, there was Maps.me; this app was also open source but became increasingly user hostile over time. Organic Maps is what happens when the users have this freedom.
2. Privacy. Even when used offline, Google Maps tracks and reports your location to Google. Organic Maps does not track and report your location to anybody.
3. Giving Back. While it is possible to suggest edits to Google Maps, these edits become part of Google's proprietary map database and can only be used in accordance with Google's ToS. This means that ultimately, Google's profits are what you are contributing to. Organic Maps, on the other hand, uses OpenStreetMap [0] and allows the user to contribute to it. Data contributed to OpenStreetMap can be freely used by anybody, for any purpose, thus benefiting all humankind rather than just one massive, US based, corporate entity that may not have humankind's interests at heart.
But then there's OpenStreetMap. Are you familiar with that? It's open data, which is sort of related to opting out of big tech. It's "free" like Wikipedia, nobody can forbid access to the data itself.
Practical benefits: Among OSM applications, Maps.me and organicmaps are more snappy. OsmAnd is a leading OSM application, and it just has a ton of options which is perhaps good for a power user but it's not streamlined.
And then the practical benefit of OSM itself is that while you often don't get as much info as Google Maps, sometimes you get stuff that Google misses. I think a big one is foot trails and stuff. Local enthusiasts like to walk them and fill them in on the map. I added a water reservoir in Berkeley once that was somehow not on Google Maps.
For me on Android:
In-car navigation - Waze + AmiGo;
Town centre navigation - Here/OsmAnd;
Searching - Google Maps;
Off-road, tracking, poi info, terrain, overview etc - OsmAnd (OpenStreetMap).
OsmAnd search UX sucks or I'd use it for that as well; the data is there.
Here and OsmAnd are both offline after initial setup, which you will do when you install them, no need to remember to manually prepare local tiles as with Google maps offline.
2. You can't download offline maps for South Korea in Google Maps. There may be other areas in the world like this.
3. OSM data is better for hiking trails in my experience.
Also Google being an internet connection assumed on in general company makes me worry a bit about being in a situation where I need to use my offline maps and finding they were wiped in an update or something.