This is an interesting discussion, but mainly for the way in which it points out the inadequacy of all maps. What I mean by that is that a map is a fixed representation of a landscape where what is included in the map is selected or rejected by the mapmakers. As non-professional mapmaker, but someone who has needed to make maps for various purposes, these truths are brought home to you when you are faced with the sudden decisions of inclusion/exclusion vs clarity of display. It’s complicated.
All maps are
• Selective in the data/features displayed, political.
• Either parochial, showing data relevant to an area or country or global showing a common set of features in a common style.
• Out of date
To expand on this. OSM is a global standard. Why should it have a special annotation for English rights of ways, ones that don't even apply in Scotland? This would be perverse: to be consistent we would need similar but not identical features for all political areas. By saying that maps are out of date means that the UK specifically, the World in general, is a dynamic place. As soon as a map is published, something changes. OSM tries to keep on top of this by having thousands of contributors and very rapid updates cycles, but even so it is full of errors & omissions. I am not sure of the update cycle of OS but I know that to buy a paper map is to buy a historical snapshot.
It’s a huge topic and one that can be discussed for ever. Both OS and OSM are excellent & complimentary products.
Coming back to the issue of English rights of way. If you know where the right of way lies, then absolutely one should download a GPX onto your GPS unit to display over either an OS or OSM background. In a small way you are on your way to being your own mapmaker, choosing information that is valuable to you for your own reasons.
Mapping is fundamentally personal.