Rings: +6 Protection vs. +5 Evasion

[HANFGEIST]

http://crawl.akrasiac.org/rawdata/HANFG ... FGEIST.txt

I was wondering if I should replace my +6 protection ring with a +5 evasion ring. I have spiny 2, so lower AC would slighty increase that damage. What do you guys and gals think?
Also does evasion help against certain spells,(i.e. you jump out of the way of a Venom Bolt)?
Does AC help in some enemy special attacks?

[radinms]

your AC doesn't affect spiny damage.
spiny 3 = 1/2 probability, 4d5 dmg

[bel]

To OP, both are good, just toss a coin and pick one. I would generally go with AC.

Evasion works against spells yes.
AC works against special attacks in the sense that (for many attacks) if AC reduces the main attack damage to 0, the special attack isn't applied, or at least has a much smaller chance of being applied.

[Sar]

You should wear both because your randart ring doesn't really do much for you - you have innate rF, MR+++++ is an overkill, elec attacks are extremely rare and you can just put it on in case you run into one, random evocable blink is not so amazingly good to keep it on all the time.

[Berder]

What Sar said. If you had to pick just one (you don't), +6 protection is better than +5 evasion given your current ac/ev. That could change if you had repel/deflect missiles, which you don't.

[HANFGEIST]

your AC doesn't affect spiny damage.
spiny 3 = 1/2 probability, 4d5 dmg

Apparently the wiki is once again OOD.
Thanks to all advisors, your help is much appreciated!

[njvack]

One time I got next to the wiki and it did like 75 damage to me. Once I learned its movement rules I got pretty good at dodging it, though.