We don't have precise usage stats but CoMaps went over Organic Maps in terms of edits sent to OSM.
So at least the users that contribute back arr mostly on CoMaps.
CoMaps feels much more active within the OSM community compared to Organic Maps that seems to be just doing their things in their own corner.
Also I took a look at their repos, Organic Maps is using Claude Code a lot, while CoMaps has a much stricter AI usage policy, and is on codeberg, an open source host instead of using Github.
I know where to place my bets.