It's hard to say although last time I looked into this literature really deeply, it seemed like distance was kind of the key. That is, most health gains could be equated by distance in that whatever gains you'd get from 1 hour of walking, epidemiologically speaking, would be accrued by running the same distance that's covered in that hour of walking (on average or whatever).

Yeah, it would be interesting to have HIIT, running and walking with the same calorie count, to see whether the type of exercise makes a difference, too.

Walking 30-60 minutes a day is basically "get a dog"