I only saw Tim's last tour, and obviously never saw Hadlee and Cairns, so i can't really comment. I also woudn't have a clue how the ball has changed over the last 30 years and how this changes things.. Hadlee was a freak, he would swing the ball anywhere. Similarly McGrath, these bowlers only needed the ball to swing a bit, and Harris is similar. We all know Johnson can swing the ball round corners, yet most of the time we see him move the ball much less.
I suppose its the difference between "swing" and "swing", where one is banana swing, and the other is a little bit through the air, which rewards bowlers in the Hadlee-McGrath mould. Our bowlers tend to be me more effective with the former, Southee is improving, but he's still not as good as a Harris, or even Hazlewood at the later, while Boult remains firmly in the former camp.