Easily Dartmoor.... or maybe the coast. Not sure.
I love Dartmoor as it's so nice to go on walks there, I love the pubs up there to and you can get a full day of adventure on Dartmoor. That being said, I do think we're lucky to have a North and South Coast in Devon and I love coastal walking. I did most of the South Coast Coastal Walk in 2019 and would love to complete the North Coast some time soon.