I haven't used Natural Atlas, but AllTrails is fine. It helps to discover good hikes, but its mapping of the trail can be bad at times. I've been on a few hikes where AllTrails wanted me to go off the marked trail or straight through lakes. Despite that, it isn't that bad if you trust the trail signage and the trail conditions over what AllTrails says.
I haven't used Natural Atlas, but AllTrails is fine. It helps to discover good hikes, but its mapping of the trail can be bad at times. I've been on a few hikes where AllTrails wanted me to go off the marked trail or straight through lakes. Despite that, it isn't that bad if you trust the trail signage and the trail conditions over what AllTrails says.