Anecdotally, I would say that flint stone walls are more common than wavy walls. I’ve see plenty of the former and none of the latter wham driving through the county.
that's not surprising. even without ever having been there i am aware of some areas of the british isles having a reputation for stone walls. but not for brick walls. which makes the question of the popularity of wavy brick walls even more interesting. how many non-wavy brick walls are there?
yes, but you also need to take into account how many homes have any brick wall at all.