Is this not basic physics looking at pivot points? If 160+ pounds is landing on your heels, the shock of that must be absorbed entirely by your knees and hips. If the same weight lands on the the front of your feet, you have the added absorption offered by your toes, ankles, and achilles tendon. That's not exactly anecdotal.
As for the long-term health effects of one or the other, that's still being debated and might be dependent on the joint health of the individual runner. See [1].
[1] http://journals.lww.com/acsm-msse/Citation/2013/12000/Forefo...