What's the difference between a poison that causes poison damage and one that causes concentrated poison damage?

In other words, what's the difference between the damage health poison and the ravage health poison?

Ravage Health reduces maximum health as well as current level of health while Damage Health reduces current level of health. I personally do not use this, but wiki mentions it may be useful against trolls and mages.

http://www.uesp.net/wiki/Skyrim:Ravage_Health