Anyone wanting to immerse themselves in the minutiae of recoil calculations will enjoy this post:

Recoil calculations

This is the most intelligent discussion of recoil I have ever read. Now if we could have the same discussion of effects of recoil versus chamber pressure on the longevity of double guns I think we could make additional intelligent decision on load selection for our beloved classic shotguns and finally answer the question of which is more destructive heavy recoil or high chamber pressure (within safe pressure limitations of course).