I think there were some tests done around the subject, the best example being a volcanic plate shield vs Grey Owlite.
There's been a lot of discussion if either the grey owlite or volcanic plate shield is better for Firestorm Citadel. I've seen people say the following things:
Volcanic plate shield can withstand 2 hits from vanaduke's mace, breaking on the third, while the owlite can only withstand 1, breaking on the 2nd.
This can be explained that the plate's normal defense is much higher than Owlite's and the mace does normal damage.
Volcanic plate can withstand almost as much gun puppy bullets as the Grey owlite can, if you stand as close as possible to a gun puppy.
This seems to imply that either volcanic plate regenerates faster or simply has more health.
Volcanic plate shield bumps zombies much farther than barbarous thorn shield.
This implies that yes, shields have varying bump distances. Nobody seems to have anything but a vague idea what that is based on.
The easiest way to test this conclusively would be to go to training hall with both those shields and test it on the spikes (piercing) or fire pit. If volcanic plate shield has more health, it should take more hits to break from either of those damage sources.
You can check the Wiki. With your previously mentioned exception it certainly seems that they all have about the same health/durability. Perhaps they weaken/break faster if they don't have as much resistance to the damage type currently being dealt to them. As for the other stats, I have no idea.