I think it's a lot more versatile
@Magnus - you can import routes from Komoot (and possibly other apps too) onto the Nyon which include all sorts of off-road bike routes and trails. You can also do this on the Kiox but this has to be linked by bluetooth to your phone and only gives turn by turn guidance rather than full maps, whereas the Nyon has inbuilt GPS and map displays.
I've got an app on my phone which gives bridleways etc (Visorando) which is free but seems to be aimed more towards walking routes. It offers search options for lots of activities (mountain bike/skiing/horse/snowshoes/canoe & kayak/hybrid bike and road bike) but choose anything other than walk and it doesn't offer anything. How much does the OS service cost - and does it offer route planning like Komoot?