OSMAnd is really good, but it's pretty slow with a clunky interface and an unpleasant theme. CoMaps has a very streamlined UI, a pleasant theme and very good performance.

I still keep both since OSM is more feature rich especially for elevation (important when cycling), but for day to day use CoMaps is the one I use.

Both are fully Open Source and use OSM data so I'm not worried much about them going to shit, though I'm under the impression CoMaps is non-profit more community built, while OSMAnd is a for small for-profit with still a community behind.