Well, I hate to reply to myself, but some testing tonight results in answers and more questions!
With only a fire bonus on my bracers, I replaced the cubed Cindercoat with Pride's Fall - that way, I could test each of the elements by only reenchanting my bracers. A fair test.
What I found is that the fire damage is doing way more damage than anticipated. Compared to either holy or lightning, the crit numbers displayed are 2.5x - 3x higher. I don't understand why, but it looks like that moots the question.
I still wouldn't mind not having to slot cindercoat... I'll try some more wit