As a active OSM contibutor with 7k+ changesets, Organic is my favorite map app I use for years traveling around the world, also donated to them. Only use GMaps for finding businesses.

Tried CoMaps, saw no reason to migrate to it at all - why migrate to basically no-name app (in terms of popularity) which is developed by who knows who (not even a Maps Me or OM devs) if Organic is totally good, has updates, stable, works well and has no ads? Have no idea what is this ad talk to be honest.

OSMAnd is nice, but too cluttered, OM is much easier to use. Only cool thing is being able to get live updates to a map if you changed something in OSM, but never actually used it for real.