Maybe this post about decay damage by Kristoffer O helps for this discussion as well:
Post#325726
...so I would guess that not all banfire/decay effects are of the same 'quality'.
BTW, is there a cap on the regeneration rate? And do they all add up (e.g. does 'casting the spell personal regeneration', 'regeneration from items', 'regeneration from a blessing effect' and an 'innate regeneration ability' always stack? Does the regeneration percentage stack additively?)