The interface is so much cleaner and soo much faster, both the UI and the map rendering, especially on some less powerful devices.

OsmAnd is full of feature and a beautiful app, but the interface is very complex and at times quite cluttered. CoMaps has more compressed map files, faster and (objective opinion) better looking render, is faster to load and uses less battery. I use them both for different goals.

CoMaps is great if you just want to open a map and see where you are, what is around you, which paths you can take, where the nearest water is and what are the landmarks around you, all without complex UI widgets and complex search, just a plain simple (beautiful) map.