So all forks of the same project. Maps.Me is not open source anymore (I think?), and CoMaps was started by a subset of the Organic Maps community that wasn't happy with the Organic Maps governance.
> What might make me switch?
Different reasons for different people, but OpenStreetMap is a great community project, for one. What I really like with those apps (I am now using CoMaps) is that they are open source, offline first and the UI is quite minimal and clean.
With CoMaps I don't think, there are any original authors involved (?). In any case I prefer organic, the original. Donated and very grateful that this app works so well (except for search where I sometimes use another app).
Google Maps will always have better POI data because they have a larger userbase and they've gamified adding POIs with the "Local Guides" badge.
The main reason to switch is to have an offline-first experience. Google Maps does not provide offline maps everywhere, e.g. South Korea. And if you've ever tried using the Google Maps app on a weak connection, it's frustrating because it still tries to download remote tiles instead of using the ones you've downloaded.
Lastly any contributions you make in OpenStreetMap will show up in Organic Maps / CoMaps for everyone.
Personally, I use Google Maps on a daily basis, but have Organic Maps and regions downloaded for travel and just switch between the two. It's good to have a reliable fallback.