I tried both and they both have their ups are downs. Some examples

Osmand+ is really slow with map tile displaying and doesn’t make the experience smooth for me. Osmand has many more features. The maps are also a bit too chaotic imo, because all POIs get displayed together.

OM is much smoother in experience but the maps only get updated once a month. It’s extra disappointing for me because I only see my changes live after a month.

I use OM dominantly, but I also keep the other one installed in case the first lacks something