Except that in a harness (even the safest ones) the damage is done to the spine, when the harness restrains the body and not the head. I have a friend whose dog died of spinal injuries while wearing a good quality harness that kept him in place. Now, granted, this was a very bad accident, and my friend lost his life too. But if you watch the videos on CFPS, the amount of displacement in the neck is HUGE, even at 30MPH. The harnesses that get high ratings do so because they do not fail, and allow the dog to become a projectile in the car. Since they (have to) use dummies in crash tests, there is no data on spinal injuries.
Over and over, I have seen accidents where dogs in solidly built crates (not wire crates) survive. The SleepPod is very well rated if you have a dog small enough for it. Kodi is not, and Panda would be borderline. My Variocage was expensive, but I know my dogs are safe. When they are in our pickup truck, which doesn't accommodate a Variocage, they ride in Ruff Tough Kennels. Also a really good choice for those "slightly larger" Havs.